GRI-02/0105
Resource Guide for Heavy-Duty LNG Vehicles, Infrastructure, and Support Operations
FINAL REPORT
March, 2002
Prepared by
Kevin L. Chandler Matthew T. Gifford Brian S. Carpenter
BATTELLE
505 King Avenue Columbus, Ohio 43201
For
Brookhaven National Laboratory
75 Rutherford Avenue Upton, NY 11973
and
Gas Technology Institute
1700 Mount Prospect Road Des Plaines, IL 60018
GRI Project Manger Mark Perry
LEGAL NOTICE
This report was prepared by Battelle as work sponsored by the U.S. Department of Energy (DOE) for Brookhaven Science Associates, LLC (Brookhaven), and Gas Technology Institute (GTI). Neither DOE, Brookhaven, GTI, members of these organizations, nor any person acting on behalf of them:
a. Makes any warranty or representation, express or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any apparatus, method, or process disclosed in this report may not infringe on privately-owned rights; nor
b. Assumes any liability with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed in this report. Furthermore, any reference to trade names or specific commercial products, commodities or services in this report does not represent or constitute an endorsement, recommendation, or favoring by the sponsors or Battelle of the specific commercial product, commodity, or service.
ii
REPORT 1. REPORT NO. 2. 3. Recipient’s Accession No. DOCUMENTATION GRI –02/0105 PAGE 4. Title and Subtitle 5. Report Date March 2002 Resource Guide for Heavy-Duty LNG Vehicles, Infrastructure, 6. and Support Operations
7. Authors 8. Performing Organization Rpt. No.
Kevin L. Chandler, Matthew T. Gifford, Brian S. Carpenter
9. Performing Organization Name and Address 10. Project/Task/Work Unit No. G003958 Battelle 11. Contr. (C) or Grant (G) No. 505 King Avenue Columbus, Ohio 43201-2693 12. Sponsoring Organization Names and Addresses 13. Type of Report & Period Covered
Brookhaven National Laboratory, P.O. Box 5000, Upton, NY 11973-5000 Gas Research Institute, 1700 South Mount Prospect Road, Des Plaines, Illinois 60018 14.
15. Supplementary Notes
16. Abstract (Limit 200 Words)
This Guide is designed to assist decision makers and fleet managers, in considering the use of liquefied natural gas (LNG) in heavy-duty vehicles. The objective of the Guide is to answer questions regarding implementation of LNG fuel in the fleet, e.g., getting started, likely costs, benefits, and lessons others have learned. This Guide also provides you with contact information for representatives of companies now using these fuels, manufacturers and suppliers of the fuels, and technical and governmental reference materials. The information in the Guide is intended to be useful for both new and existing end-users of heavy-duty LNG vehicles, so that operations can be initiated or conducted in a cost-effective manner with minimal disruptions related to the new fuel technology.
17. Document Analysis
a. Descriptors Liquefied natural gas, LNG
b. Identifiers/Open-Ended Terms Fleet Management, LNG vehicles, LNG, LNG Infrastructure, LNG Maintenance and Support, LNG Implementation
c. COSATI Field/Group
18 Availability Statement 19 Security Class (This Report) 21. No. of Pages
Unclassified Availability Unlimited 20. Security Class (This Page) 22. Price
Unclassified
iii Acknowledgments/List of Participants
The authors wish to acknowledge the support and contributions of Jim Wegrzyn from Brookhaven National Laboratory and Michael Gurevich of U.S. Department of Energy’s Office of Heavy Vehicle Technology. The authors also gratefully acknowledge the contributions of Mark Perry, Lou Lautman, and Rajeana Gable of Gas Technology Institute. Thanks also to Denny Stephens and Helen Latham from Battelle.
The support for this effort from the industry has been significant and is gratefully acknowledged. Several industry contributors and reviewers of this report are listed below:
Charles Powars, St. Croix Research Gary Pope, USAPro Hank Seiff, Natural Gas Vehicle Coalition Cindy Sullivan, Bob Nguyen, California Air Resources Board Leslie Eudy, National Renewable Energy Laboratory Stan Taylor, Blue Fuels Ken Henrie, United Parcel Service Don Keski-Hynnila, Detroit Diesel Corporation Erik Neandross, Gladstein & Associates Steve Gregory, ATC-Tempe Carlos deLeon, City of Tempe, Arizona James Ortner, Orange County Transit Authority Darryl Spencer, Dallas Area Rapid Transit George Kalet, Patrick Hutson, NexGen Jim Harger, ENRG Stan Sasaki, Raley’s Paul Gagnon, Jerry Simmons, Waste Management
iv Reporting Comments
The authors have attempted to present complete and accurate information. However, with all reports, there may be unintended omissions and errors that evade the editing process. Please report any omission or error to the following people. If there are future updates to this report, changes and additions will be made as appropriate and as resources allow.
Mark Perry
Gas Technology Institute 1700 South Mount Prospect Road Des Plaines, IL 60018 Telephone: (847) 768-0787 Fax: (847) 768-0501 e-mail: [email protected] or
Kevin Chandler
Battelle 505 King Avenue Columbus, OH 43201 Telephone: (614) 424-5127 Fax: (614) 424-5069 e-mail: [email protected]
v Table of Contents
Page Acknowledgments/List of Participants...... iv Reporting Comments ...... v Acknowledgments/List of Participants...... v Acronym List ...... xii Introduction ...... 1 Organization of Resource Guide...... 1
SECTION 1 - THE BASICS What’s In This Section? ...... 3 Why Alternative Fuels? ...... 3 What Is LNG?...... 5 How Do We Get Started?...... 6 How Do We Resolve LNG Problems? ...... 14 What Are the Safety Considerations for LNG Vehicle Operations? ...... 15 Is LNG Readily Available? ...... 19 What Will This Cost Me?...... 21 Where Can I Find More Answers?...... 23
vi Table of Contents (Continued)
Page
SECTION 2 - THE SCIENCE & DETAILS What’s In This Section? ...... 4 Why Alternative Fuels? ...... 24 Alternative Fuel Descriptions ...... 25 Legislative Drivers...... 28 Incentives ...... 33
What Is LNG?...... 34 Natural Gas Characteristics...... 35 Natural Gas as a Vehicle Fuel...... 36 LNG Background...... 37 LNG Characteristics...... 37 LNG Saturation...... 41 LNG Vehicles ...... 45 LNG Fueling Stations ...... 49 Weathering of LNG Fuel ...... 54 LCNG Characteristics...... 55
How Do We Get Started?...... 57 Equipment and Operational Differences with LNG ...... 58 Implementation Timeline...... 61 Build the LNG Implementation Team ...... 64 Start Early to Collect Data and Build a Network...... 65 Build An Implementation Strategy and Plan (The Roadmap)...... 68 Corporate Commitment, Communication, and Promotion...... 69 The Purchasing Process ...... 70 Facilities (Fueling, Maintenance, and Vehicle Storage)...... 75 Planning for Early Operations and Problems...... 77 Training and Safety...... 77
How Do We Resolve LNG Problems? ...... 78 Make Sure Adequate Information is Available ...... 78 Implement Practices to Prevent Problems ...... 79 Prepare for Possible Problems ...... 80 Vehicles...... 80 Fueling Stations ...... 81 Other Facilities...... 81 Optimization ...... 81
vii
Table of Contents (Continued)
Page
What Are the Safety Considerations for LNG Vehicle Operations? ...... 81 Effects of LNG Characteristics on Safety...... 82 LNG Codes and Standards...... 83 Potential Hazards Associated with LNG ...... 85 Vehicle Specifications ...... 86 Vehicle Operation and Maintenance...... 88 Fueling Facilities...... 89 Maintenance and Parking Facilities...... 92 Transporting LNG...... 94 Personal Protective Equipment...... 95 Emergency Response...... 96 Safety and Training...... 98
Is LNG Readily Available? ...... 101 North American LNG Production and Distribution...... 101 Current Availability vs. Potential Availability ...... 101 LNG Motor Fuel Production Plants...... 103 Local Availability Issues...... 104 Sources of LNG ...... 104 Issues to Consider for LNG Availability ...... 105 Fuel Use and Delivery Strategy ...... 105 Fuel Purchasing Strategy ...... 106 LNG Distribution Company Profiles...... 106 LNG Fuel Station Design and Construction Suppliers...... 106
What Will This Cost Me?...... 108 Fuel Costs...... 108 Vehicle Costs ...... 109 Fueling Station Costs ...... 110 Facility Modifications...... 111 Fleet Cost Summaries ...... 112 Training...... 113 Personnel...... 114 Extra Costs at Start-Up ...... 114 Long-Term Operational Cost Increases...... 114 Vehicles...... 115 Facilities – Fueling, Maintenance, and Others...... 115 Operations and Training ...... 115
viii Table of Contents (Continued)
Page
Where Can I Find More Answers?...... 116 Fleet Experiences...... 116
List of Tables
Table 1-1. The Must-Have List of Reports for LNG...... 10
Table 1-2. The Must Have List of Web Site Resources ...... 11
Table 1-3. Sponsors of Conferences and Meetings that Regularly Include LNG Vehicles ...... 11
Table 1-4. General Outline of the Implementation Strategy and Plan (The Roadmap) ...... 12
Table 2-1. EPA Emission Standards for Heavy Duty Engines...... 30
Table 2-2. Average Natural Gas Composition in the U.S...... 36
Table 2-3. Chemical Properties of Natural Gas and Other Fuels ...... 40
Table 2-4. The Must-Have List of Reports for LNG...... 67
Table 2-5. The Must Have List of Web Site Resources ...... 68
Table 2-6. Sponsors of Conferences and Meetings that Regularly Include LNG Vehicles ...... 68
Table 2-7. General Outline of the Implementation Strategy and Plan (The Roadmap) ...... 69
Table 2-8. Current Chemical Facilities Producing LNG for Transportation in the U.S...... 103
ix Table of Contents (Continued)
Page
List of Figures
Figure 1-1. LNG Bus at OCTA in Orange, California ...... 4
Figure 1-2. LNG Fueling Station at Taormina Industries...... 7
Figure 1-3. LNG Transit Bus at DART in Dallas, Texas ...... 13
Figure 1-4. LNG Fueling of a Transit Bus...... 18
Figure 1-5. Locations of LNG Production Plants in U.S...... 20
Figure 2-1. Growth of Natural Gas Vehicles Over the Past 10 Years ...... 25
Figure 2-2. Greenhouse Effect...... 30
Figure 2-3. Boiling Points of Industrial Gases at Atmospheric Pressure ...... 38
Figure 2-4. The Saturation Curve for Natural Gas (100% methane) Defines the Conditions where the Liquid and Vapor Phases Can Coexist ...... 43
Figure 2-5. Pressure-Density Conditions of LNG Fuel Systems...... 44
Figure 2-6. Temperature-Density Conditions of LNG Fuel Systems...... 44
Figure 2-7. LNG Trucks at Raley’s in Sacramento, California ...... 46
Figure 2-8. LNG Yard Tractor at Raley’s in Sacramento, California ...... 46
Figure 2-9. LNG Fuel System...... 47
Figure 2-10. LNG Fuel System Schematic...... 50
Figure 2-11. Simplified LNG Fueling Station ...... 51
Figure 2-12. LNG Fueling Station at Raley’s in Sacramento, California...... 51
Figure 2-13. LNG Fueling Station at City of Tempe, Arizona...... 51
Figure 2-14. LNG Fuel Dispenser at OCTA in Garden Grove, California...... 53
Figure 2-15. LNG Fueling Port on a Transit Bus ...... 53
Figure 2-16. LNG Fueling Station at Waste Management in Washington, Pennsylvania, Station Includes LCNG Capability and Dispenser...... 56
x Table of Contents (Continued)
Page
List of Figure (Continued)
Figure 2-17. Piping and Control Equipment on a Vehicle LNG Tank ...... 59
Figure 2-18. LNG Vehicle Tanks Mounted at Rear of Transit Bus Above Engine...... 59
Figure 2-19. LNG Vehicle Tank Saddle Mounted on a Refuse Truck ...... 60
Figure 2-20. Maintenance Facility at Waste Management in Washington, Pennsylvania ...... 61
Figure 2-21. LNG Shuttle Bus in Austin, Texas...... 73
Figure 2-22. LNG Refuse Truck...... 74
Figure 2-23. Fire Suppression Chemical Storage at an LNG Fueling Station...... 90
Figure 2-24. Combustible Detection System Alarm Strobes Above Door Opening ...... 90
Figure 2-25. Signage at an LNG Fueling Station in Austin, Texas ...... 91
Figure 2-26. LNG Fueler Wearing Appropriate Protective Equipment ...... 95
Figure 2-27. LNG Processing Facility...... 102
Figure 2-28. Bulk LNG Delivery to a Fuel Station ...... 102
Figure 2-29. Locations of LNG Production Plants in U.S...... 103
Figure 2-30. LNG Refuse Truck at Taormina Industries...... 110
Figure 2-31. LNG Fueling Station at DART in Dallas, Texas ...... 111
xi Abbreviation List
A&E—Architecture and Engineering AFDC—Alternative Fuel Data Center AFV—Alternative fuel vehicle AMFA—Alternative Motor Fuels Act of 1998 ANL—Argonne National Laboratory APTA—American Public Transportation Association ASME—American Society of Mechanical Engineers BNL—Brookhaven National Laboratory BTS—Bureau of Transportation Statistics BTU—British Thermal Units C—Celsius CAAA—Clean Air Act Amendments of 1990 CARB—California Air Resources Board CEC—California Energy Commission CMAQ—congestion mitigation and air quality CNG—compressed natural gas CO—carbon monoxide CO2—carbon dioxide DOE—U.S. Department of Energy DOT—U.S. Department of Transportation DPF—diesel particulate filter EIA—Energy Information Administration EPA—U.S. Environmental Protection Agency EPAct—Energy Policy Act of 1992 F—Fahrenheit Gal—gallon GAO—General Accounting Office GGE—gasoline gallon equivalent GHG—greenhouse gases GREET—Greenhouse Gases, Regulated Emissions, and Energy use in Transportation GRI—Gas Research Institute GTI—Gas Technology Institute GTL—gas-to-liquid process H2—hydrogen HC—hydrocarbons HHV—higher heating value IC—internal combustion ICTC—Interstate Clean Transportation Corridor IGT—Institute of Gas Technology ILEV—inherently low emission vehicle IPCC—Intergovernmental Panel on Climate Change ISTEA—Intermodal Surface Transportation Efficiency Act of 1991 kg—kilogram kPa—kiloPascal
xii LCNG—liquefied to compressed natural gas LEV—low emission vehicle LFL—lower flammability limit LHV—lower heating value LNG—liquefied natural gas LPG—liquefied petroleum gas (i.e., propane) MMcf—million cubic feet (i.e., of gas burned) MPa—megaPascals MSDS—material safety data sheets NCSL—National Council of State Legislatures NFPA—National Fire Protection Association NGV—natural gas vehicle NGVC—Natural Gas Vehicle Coalition NMHC—non-methane hydrocarbons NOx—oxides of nitrogen NRU—nitrogen rejection units NREL—National Renewable Energy Laboratory OEM—original equipment manufacturer OTT—DOE’s Office of Transportation Technologies OHVT—DOE’s Office of Heavy Duty Vehicles ORNL—Oak Ridge National Laboratory PM—particulate matter (i.e., soot) PMI—preventive maintenance inspection Ppm—parts per million Psi—pounds per square inch Psig—pounds per square inch (gauge) RLM—refrigerated liquid methane SAE—Society of Automotive Engineers Scf—standard cubic feet SOP—standard operating procedure SULEV—super ultra low emission vehicle TAC—toxic air contaminant TEA-21—Transportation Equity Act for the 21st Century (issued 1998) THC—total hydrocarbons ULEV—ultra low emission vehicle ULSD—ultra-low sulfur diesel
xiii Introduction
This publication, entitled Resource Guide for Heavy-Duty LNG Vehicles, Infrastructure, and Support Operations, is designed to assist the decision maker and/or fleet manager, in considering the use of liquefied natural gas (LNG) in heavy-duty vehicles. The objective of the guide is to answer questions regarding implementation of LNG fuel in the fleet, e.g., getting started, likely costs, benefits, and lessons learned. This guide also provides contact information for representatives of companies now using these fuels, manufacturers and suppliers of the fuels and supporting equipment, and technical and governmental reference materials. The information in the guide is intended to be useful for both new and existing end-users of heavy-duty LNG vehicles, so that operations can be initiated or conducted in a cost-effective manner with minimal disruptions related to the new fuel technology.
This guide is unlike other publications and Internet sites concerning alternative fuels. These sources concentrate on selection of alternative fuels, development of fueling station equipment, or procedures to apply for available funding. The unique feature of this guide is that after providing brief background information concerning alternative fuels, it focuses on LNG and provides implementation guidance for the decision maker, fleet manager, or end-user. This includes planning and handling issues that can occur before and during purchase decisions, after the point of sale of equipment or acceptance of funding, and after the vehicles are on the road. However, this guide is not intended to advocate the use of LNG over other possible alternative fuels (see more details in the chapter titled Why Alternative Fuels?). For those fleet managers who have already decided to consider using LNG, this Resource Guide will help to anticipate the issues and navigate the maze to the selection of fuel, successful installation of infrastructure, and deployment of LNG-fueled vehicles in the fleet.
Organization of Resource Guide
The Resource Guide is divided into three sections: Section 1−The Basics, Section 2−The Science and Details, and Section 3−The Appendix. For easy cross-referencing, topics in sections 1 and 2 have the same top-level headings.
• The Basics section is aimed at the decision makers and provides summaries of the information needed to make the decisions and referrals are made to greater detail on each subject in Section 2, if desired.
• The Science and Details section is focused on the information and support needs of fleet managers and personnel. This section covers the same subjects as The Basics but provides historical background concerning LNG, information regarding the fuel’s performance, expanded detail, lessons learned, technical discussions and references, contacts for suppliers, references to individuals and Web sites, actions to avoid, and “how-to’s.”
1 • The Appendix section contains a listing of technical documents, technical papers reporting on a variety of LNG fleet experiences, issues, standards, federal and state regulations, and safety assessments; LNG-related periodicals; web sites; and fleets currently using LNG.
Section 1 − The Basics Section 2 − The Science Section 3 − The Appendix and Details - Why Alternative Fuels? - Related Documents - What Is LNG? Topics in this section are the same as in - LNG-Related Periodicals Section 1 but covered in more detail. - How Do We Get Started? - Helpful Web Sites - How Do We Resolve LNG - LNG Fleets Problems? - What Are the Safety Considerations For LNG Vehicle Operations? - Is LNG Readily Available? - What Will This Cost Me? - Where Can I Find More Answers?
This guide is a joint effort between the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory (BNL) and the Gas Technology Institute (GTI). BNL is a DOE national laboratory, which conducts basic and applied research in the physical, biomedical, and environmental sciences as well as in selected energy technologies. The guide is supported through DOE’s Office of Heavy Vehicle Technologies. GTI is the combined company that joins the resources and strong technological heritage of the Gas Research Institute (GRI) and the Institute of Gas Technology (IGT). GTI is a problem-solving organization focused on developing practical technologies and solutions for natural gas producers, refiners, chemical facilities, pipelines, and a wide range of natural gas users, including utilities and industrial clients.
Web Site References: Gas Technology Institute: www.gastechnology.org Brookhaven National Laboratory: www.bnl.gov U.S. Department of Energy, Office of Transportation Technologies: www.ott.doe.gov Natural Gas Vehicle Coalition: www.ngvc.com
Finally, this Resource Guide is intended to be a useful tool, but is only a starting point for information on using LNG. This report provides resources available via personal contacts, the Internet, accessible reports, companies now using LNG, and information from those who have experienced start-up.
2
Topic, Page
Why Alternative Fuels? 3 SECTION 1 What Is LNG? 5
How Do We Get Started? 6
How Do We Resolve LNG Problems? 14 THE BASICS
What Are the Safety Considerations For LNG Vehicle Operations? 15
Is LNG Readily Available? 19
What Will This Cost Me? 21
Where Can I Find More Answers? 23
What’s In This Section?
This section provides a brief summary of the major topics listed in the box above and is intended to be most useful to company decision makers and key personnel. Section 2 contains additional details and is designed to assist fleet personnel in implementing the program.
Why Alternative Fuels?
Alternative vehicle fuels have been available as long as gasoline and diesel fuels. Two alternative fuels—natural gas and electricity—have been used for vehicle propulsion since the first automobiles became available, but gasoline and diesel fuels quickly became the fuels of choice nearly 100 years ago. Today, transportation vehicles use 68% of all petroleum consumed
Over the past 12 years, the return to alternative fuels has been accelerating because of environmental and energy security concerns.
The definition of alternative fuels may vary slightly depending on the state in which the vehicle is used. In general, alternative vehicle fuels in use today include natural gas (compressed and liquefied), alcohol fuels (ethanol and methanol), propane, electricity, cleaner burning diesel (e.g., biodiesel, natural gas-derived diesel fuel – Fischer-Tropsch diesel), and, most recently, hydrogen for fuel cells. Blends of these fuels with gasoline or diesel fuel, as well as with other chemicals, may also be considered part of the alternative fuels group. These fuels are currently powering a variety of vehicles, including heavy-duty trucks, garbage packers and dump trucks, snowplows, package delivery vans, buses, taxicabs, and passenger cars.
Government regulations to reduce air pollution and public concerns regarding harmful emissions from transportation vehicles are the major reasons why the use of alternative vehicle fuels is increasing. Using alternative fuels in transportation vehicles can reduce air pollution and reduce the nation’s dependence on foreign oil, because most of the alternative fuels are plentiful in the U.S.
Provisions of the Alternative Motor Fuels Act of 1988 (AMFA), the Clean Air Act Amendments of 1990 (CAAA), the Energy Policy Act of 1992 (EPAct), and other federal and state legislation require a gradual transition for some fleets from fossil fuels, such as gasoline or diesel, to alternative fuels. These regulations also include requirements for monitoring emissions and providing incentives to potential users of alternative fuel vehicles. Two federal agencies, the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Energy (DOE), have enabled and promoted the movement to alternative fuel vehicles. Many states have regulations and incentive programs to increase the use of alternative vehicle fuels. The result is that emission regulations are expected to be much stricter beginning in 2007.
Natural gas is a clean-burning alternative transportation fuel available in adequate quantities today—producing significantly lower emissions than required by the Clean Air Act Amendments of 1990. Natural gas vehicles (NGVs) have been certified to perform in compliance with all current environmental emission standards, including standards limiting particulate matter, carbon monoxide, and oxides of nitrogen. Figure 1-1 shows an LNG bus from Orange County Transportation Authority in Orange, California.
3
Figure 1-1. LNG Bus at OCTA in Orange, California
A side benefit of the pressures to convert U.S. fleets of light- or heavy-duty vehicles to alternative fuels is that manufacturers have found ways to reduce exhaust emissions from conventional vehicles (i.e., gasoline and diesel powered) over the past l5 years. The downside of this aspect is that, despite the legislation and incentives, consumption of petroleum-based fuels continues to increase, further entrenching our dependence on foreign oil. The purchase of alternative fuel vehicles has increased significantly, but few of the light- and medium-duty alternative fuel vehicles purchased are dedicated vehicles. Dedicated vehicles can only operate on the alternative fuel that they were designed for. Most of the medium- and light-duty alternative vehicles are bi-fuel (operates on the alternative fuel or conventional fuel) or dual-fuel (can use an alternative fuel, conventional fuel, or some combination). Surveys indicate that most bi-fuel and duel-fuel vehicles are operating almost exclusively on gasoline or diesel because of the lack of alternative fuel filling stations.
To encourage the use of alternative fuels, governmental agencies and other sources offer incentives to vehicle manufacturers, sales outlets, and buyers to promote the use of alternative fuels. Current and potential future incentive programs are described on the following Web sites:
• Alternative Fuel Data Center: www.afdc.doe.gov • Clean Cities: www.ccities.doe.gov • Natural Gas Vehicle Coalition: www.ngvc.org
Once a company has decided to use an alternative fuel in the fleet, the first executive decision to make is the selection of the alternative fuel best suited for your company’s operation. Each of the alternative fuels mentioned earlier has positive points and potential downsides. The major variables among the alternative fuels are (1) the security of the fuel supply and proximity of the fuel supplier, (2) the availability of on-site space for installing the fuel supply facility or access to a public fuel supply facility, (3) potential complications of retrofitting the engines or
4 purchasing new vehicles, (4) training required for drivers, maintenance and fueling personnel, (5) possible incentives, grants, or rebates from federal or state funds or vehicle manufacturers, and (6) the estimated costs of all of these factors. This Resource Guide assumes that you have thought through these variables and decided to more thoroughly consider the use of LNG in your fleet.
What Is LNG?
Liquefied natural gas (LNG) is the liquid form of natural gas. LNG is essentially the same as the natural gas used to heat homes, commercial buildings, and plants. Natural gas is composed primarily of methane, with smaller amounts of other hydrocarbons such as ethane, propane, butane, pentane, and gases such as nitrogen and carbon dioxide. Natural gas, with an octane rating of 130, is well suited for spark-ignited internal combustion engines, but is not as well suited for compression ignition cycle engines (diesel engines) without some assistance in starting the combustion process such as using a small amount of diesel fuel (dual-fuel engines) or adding spark plugs.
The process of liquefying gases was invented in the early 1900’s to separate components of atmospheric gases by cooling air in stages under pressure until the constituents (e.g., oxygen, nitrogen) condensed to a liquid form. Today, LNG is purified before liquefaction, i.e., elements in pipeline gas (such as condensable water, carbon dioxide, and odorants) are removed. Then, refrigeration at cryogenic temperatures and/or depressurization is used to liquefy the natural gas. This process removes some of the heavier hydrocarbons, leaving mostly methane (85 to 99 percent). The resulting LNG is a clear and odorless cryogenic liquid that is non-toxic, non- corrosive, and non-carcinogenic. Most LNG is produced at storage locations operated by natural gas suppliers and at cryogenic extraction plants in gas-producing states.
Compressed natural gas (CNG), like LNG, is the same fuel used for home heating and cooking. CNG is different from LNG in that it is a gas that is compressed to nominal pressures as high as 3,600 pounds per square inch (psi). (Pressures can be even higher when taking temperature compensation effects into account.) As noted earlier, this Guide is not advocating the use of LNG over any other alternative fuel such as CNG. The decision between LNG and CNG, for example, is usually determined by comparing the space needed for fueling infrastructure, the availability of the fuel and the vehicles, the energy density of the two fuels, weight of the vehicle fuel tanks, fuel cost, and range allowed by the on-board fuel supply.
LNG has a lower energy density than gasoline and diesel, but a higher energy density than CNG and many other alternative fuels. This means that LNG has less energy per volume than gasoline or diesel fuels. (There is a 1.55 to 1 energy ratio when gasoline is compared to LNG and a 1.67 to 1 energy ratio when diesel is compared to LNG).
Liquefied to compressed natural gas (LCNG) is produced by pumping LNG up to a selected pressure level and then vaporizing the liquid through a heat exchanger (vaporizer). It is more efficient and faster to pressurize natural gas in liquid form. LCNG can be pressurized via a
5 relatively small cryogenic pump (e.g., basketball size). LCNG can be used for light- and heavy- duty vehicles and its fueling stations and operations are similar to those for LNG. Although this Resource Guide concentrates on LNG vehicles, fuels, and facilities, understanding the implications of choosing LCNG can be helpful for decision makers. For example, if your fleet operating site is located far from a pipeline (such as at a remote national park) the liquid version of the fuel may be more practical to transport. At the same time, the more established CNG technology may be more readily available, especially if your fleet consists largely of light- duty vehicles. A fleet in this situation could utilize LCNG to take advantage of the higher energy density of LNG for transporting the fuel and the convenience of CNG for storage of fuel on- board the vehicles. LCNG capabilities can also be added to an LNG fueling station with a modest amount of station modification. This option may be ideal for fleets operating both CNG and LNG vehicles.
How Do We Get Started?
Many demonstration projects for fleets of trucks and buses using LNG in commercial operations have been completed or are underway. During these demonstrations, valuable information has been collected from participating company personnel. Data on operations, maintenance, vehicle performance, and emissions have been analyzed. The engineers and fleet managers also willingly identify lessons learned from each demonstration. Experience has shown that successful implementation of LNG (or any new technology) in fleet operations is built on planning, strong leadership, and commitment.
One of the major lessons learned from LNG vehicle operations is to have realistic expectations of the implementation process and the costs required for start-up and operation. Implementing any major new technology within a fleet will require additional costs, time, and effort. Planning for this extra effort and cost will be the key to avoiding delays and budget overruns. Although some of these costs can be recovered through incentives, it is rare that any of these projects proves cost-effective during the first few years. Beyond being expensive at start-up, such projects are often slow moving, taking a long time to implement and adjust to the new vehicles and related operations. In short, LNG implementation is not a simple process, and it rarely comes with financial benefits at the beginning, but there are reasons that make LNG implementations worth doing (as discussed earlier in Why Alternative Fuels?). Some of the most difficult issues in the beginning come down to the newness of the technology and the lack of information available for making good decisions.
Equipment and Operational Differences with LNG
There are many details about the technical changes involved with implementing LNG vehicle operations that you should be aware of before deciding to implement LNG in your fleet. In general, when using new technology like LNG, there will be fewer options available. This will apply to engines, vehicle platforms, fuel suppliers, and many other aspects of LNG operation. Using engines as an example, the heavy-duty natural gas engine offerings from OEMs do not have as many horsepower and torque settings available as conventional heavy-duty engines do.
6 In addition, this new technology may not perform as well as the conventional systems you have used in the past. Again, using the example of engines, dedicated natural gas engine technology is not as efficient as its diesel counterpart (spark ignition versus compression ignition) especially at low loads and when in idle mode. The natural gas vehicle industry is working on expanding the available options and improving technology performance, but it will take some time for LNG to reach the technological maturity of conventional fuels. Figure 1-2 shows an LNG fueling station in Southern California. Section 2 includes further details regarding the technical differences between LNG and conventional technologies.
Figure 1-2. LNG Fueling Station at Taormina Industries
Implementation Timeline
The implementation of LNG vehicles usually progresses in phases:
• Early planning – collect data, make contacts, and make a plan to move forward. • Program implementation – complete the purchase process including specifying, ordering, and installing LNG equipment, complete the first round of training activities. • Start-up – resolve initial problems in the systems, get the vehicles and support equipment up and running on a regular basis, need focus on adequate training and safety procedures. • Optimization – track and study the vehicle and facility operations, implement changes as appropriate to optimize the operation, resolve problems and issues, integrate training for LNG into standard training activities.
These phases may take two to four years to complete depending on the timing and availability of equipment and support. Running across these time phases are several specific activity
7 categories. Introduction of the new vehicles should be made over time. Furthermore, time must be allowed to troubleshoot, provide training, and educate the staff, management, and local officials. The LNG implementation process is discussed in brief in this subsection by the following categories. Further details regarding specific strategies for LNG implementation are included in Section 2.
• Build the LNG implementation team • Start early to collect data and build a network • Build an implementation strategy and plan • Corporate commitment, communication, and promotion • The purchasing process • Planning for early operations and problems • Training and safety
Build the LNG Implementation Team
This LNG implementation team will be the group that leads every phase and aspect of the LNG implementation. This team will work through the purchasing process and prepare for early operations and problems. As the vehicles and infrastructure come online, this team will evolve from implementation to optimization of the operation of the vehicles and infrastructure, and work to resolve ongoing issues. Once the LNG equipment is up and running, some of the problems may be complex and require study and data collection in order to address each problem properly. This team will lead these troubleshooting activities.
Start Early to Collect Data and Build a Network
Everything about LNG may be new to you at the beginning. It is important to start early in the process of considering the implementation of LNG vehicles by collecting data, building a network of experts, vendors (especially the original equipment manufacturers of the LNG systems), and other fleets, and building the implementation strategy (or roadmap). The hardest parts of implementing LNG vehicles are getting started, finding resources (funding, reports, and web sites for information and background), and finding experts and vendors to begin the process of developing your own LNG vehicle and infrastructure operation experts. At the beginning, what you lack most is experience on which to base decisions.
Before deciding whether or not to implement LNG, you should learn as much as you can about the specific changes that you would need to execute and consider the effects that these changes would have on your fleet. In order to do this, you will need to collect all the information necessary to understand the LNG fuel, LNG technologies, and the best strategies for implementing LNG within your particular fleet. Here are some suggested sources:
8 • Access all the relevant web sites for background information needed to make good decisions (note: many references to government, commercial, and trade association web sites are included throughout this Resource Guide). Tables 1-1 and 1-2 provide a must- have list of reports and web sites that should be considered a starting point. • Analyze your service routes to determine the number of vehicles needed for your service area and a technical description of your service duty cycle from the vehicle operation perspective. • Examine your budget and determine what can be allocated for the new LNG vehicles. • Attend LNG, natural gas, and other AFV conferences and meetings where you can learn more as well as develop contacts and identify support groups; it is especially important to talk with OEM representatives, fuel providers, and LNG users at conferences and exhibits; actively look for funding sources and work to understand available credits. Table 1-3 provides a list of some conference sponsors that should be considered. • Review environmental and building regulations prior to site planning to accommodate the new fueling infrastructure. • Contact your local building codes officials and the fire marshal in your area; make sure these officials are included in planning for facility modifications and additions in preparation for LNG. • Study your facility’s site drawings to anticipate modifications and additions. • Consult with an experienced Architectural & Engineering (A&E) firm with relevant experience specifically in LNG to provide options and accurate cost estimates. • Obtain descriptions of site modifications, needed infrastructure, and safety equipment needed for your site(s). • Take tours of similar facilities where LNG facilities have been installed. • Purchase or gain access to alternative fuels technical manuals for vehicles and infrastructure. • Attend training courses on LNG vehicles and infrastructure.
Section 3−The Appendix includes listings of reports, web sites, training material, and newsletters and magazines that include information regarding LNG vehicles and infrastructure.
Build An Implementation Strategy and Plan (The Roadmap)
The development of the implementation and strategy plan is critical especially in the early stages of planning for LNG. This plan should describe all of the activities and timing, the business plan for the LNG program (how much money is needed and where is the money going to come from), and an overview of responsibilities of staff for each aspect of the program. This plan needs to be flexible and will need to be modified many times before the LNG operation becomes routine. One of the most important parts of this plan will be the definition of success of the LNG implementation and operation. The plan will need to describe what the goals of the program are and what success is, so that you will know when you have it.
9 Table 1-1. The Must-Have List of Reports for LNG
Topic/Report Report Number Where to Order General Information Liquefied Natural Gas: Alternative Fuel of Choice CD-ROM www.nexgenfueling.com NGV Resource Guide www.ngvc.org The Clean Fuels and Electric Vehicles Report www.energy-futures.com Funding/Getting Started Guidebook for Evaluating, Selecting, and Implementing Fuel TCRP Report 38 www.trb.org Choices for Transit Bus Operations Liquefied Natural Gas for Heavy-Duty Transportation www.gastechnology.org Natural Gas Buses: Separating Myth from Fact NREL/FS-540- www.afdc.doe.gov 28377 Natural Gas Vehicle Purchasing Guide www.afdc.doe.gov Fleet Start-Up Experiences at the AFDC Several www.afdc.doe.gov/pdfs Vehicles Reference Guide for Integration of Natural Gas Vehicle Fuel GRI-02/0013 www.gastechnology.org Systems Heavy Vehicle and Engine Resource Guide NREL/TP-540- www.afdc.doe.gov 31274 Recommended Practices for LNG Powered Heavy-Duty J2343 www.sae.org Trucks Vehicle Maintenance and Operating Manuals From OEMs Fueling Station and Facilities Risk Management Plan Guideline for LNG Vehicle Fueling GRI-98/0245 www.gastechnology.org Stations Qualitative Risk Assessment for an LNG Refueling Station INEEL/EXT-97- www.inel.gov and Review of Relevant Safety Issues 00827 rev 2 Clean Air Program: Design Guidelines for Bus Transit DOT-FTA-MA- www.ntis.gov Systems Using Liquefied Natural Gas (LNG) as an 26-7021-97 Alternative Fuel Operating Manuals for Safety Equipment including servicing From OEMs procedures for combustible gas detectors Safety and Training Introduction to LNG Safety www.ch-iv.com Clean Air Program: Liquefied Natural Gas Safety in Transit DOT-FTA-MA- www.ntis.gov Operations 90-7007-95-3 Introduction to LNG for Personnel Safety X08614 www.aga.org Introduction to LNG Vehicle Safety GRI-92/0645 www.gastechnology.org Clean Air Program: Summary of Assessment of the Safety, DOT-FTA-MA- www.ntis.gov Health, Environmental and System Risks of Alternative Fuel 90-7007-95-1 Standard for Liquefied Natural Gas (LNG) Vehicular Fuel NFPA 57 www.nfpa.org Systems Standard for the Production, Storage, and Handling of NFPA 59A www.nfpa.org Liquefied Natural Gas (LNG) Proceedings of Liquefied Natural Gas Vehicle Systems: www.nexgenfueling.com Training School
10 Table 1-2. The Must Have List of Web Site Resources
Web Site Source Web Site Alternative Fuel Data Center www.afdc.doe.gov Clean Cities www.ccities.doe.gov Natural Gas Vehicle Coalition www.ngvc.org EPA Office of Technology and Air Quality www.epa.gov/otaq Gas Technology Institute www.gastechnology.org Alternative Fuel Vehicle Fleet Buyer’s Guide www.fleets.doe.gov CARB Moyer Program arbis.arb.ca.gov/msprog/moyer/moyer.htm Society of Automotive Engineers www.sae.org Natural Gas Vehicle Institute www.ngvi.org Alternative Fuels Training Consortium naftp.nrcce.wvu.edu
Table 1-3. Sponsors of Conferences and Meetings that Regularly Include LNG Vehicles
Meetings/Sponsors Web Site Natural Gas Vehicle Coalition www.ngvc.org Clean Cities, national and local www.ccities.doe.gov Society of Automotive Engineers www.sae.org American Public Transportation Association www.apta.com
Another key aspect of this plan is how you phase-in the LNG operation. Having vehicles without fuel or fuel station is not useful. In general, you want facility modifications and installation of the fuel station before anything else. You will want to make sure fuel will be available before or about the time that the LNG vehicles arrive. Training is extremely important and should start well before any of the equipment arrives on-site. You may want to have only a few vehicles arrive at the beginning so that the fueling, facility, and vehicle LNG systems can be checked out and changes made as needed.
Table 1-4 provides a general outline of the implementation strategy and plan (The Roadmap). This document is intended to evolve over time. In the beginning, the document can be used to define the work to be completed. As progress is made, this document can be used to track progress and define new tasks as the need arises. This plan should be defined to best suit your needs. Also, this plan should be updated on a regular basis as the implementation team meets over time.
11 Table 1-4. General Outline of the Implementation Strategy and Plan (The Roadmap)
Introduction/Background – describe the general factors pushing the use of LNG Objectives of the LNG Program – success will be based on this The Implementation Team – describe the staff needed to be involved and responsibilities Business Plan – estimated costs of the program and where the money is going to come from Operations – describe the expected use of the LNG vehicles Vehicles – describe the potential options of technology to choose from Fuel Purchase – describe the fuel requirements including how much, source, and cost Support Infrastructure – on-site fueling, facility modifications Safety – risk management and procedures Training, Training, Training – every impact of LNG operation must be incorporated into training programs Phase-In Strategy and Timeline – description of overall timing strategy and progress to date Action Items – track action items defined and progress towards completion
Corporate Commitment, Communication, and Promotion
Corporate commitment is critical to the success of the LNG implementation. This commitment sets the tone for the organization. Commitment means using funds, personnel, and work time, as well as patience and persistence to absorb this new technology into day-to-day operation. Once the Implementation Strategy and Plan has been completed, this plan needs to be made available to the senior corporate members of the company as well as managers and staff for review, comment, and buy-in. Everyone in the organization needs to eventually buy-in to the LNG implementation if it is to be successful. This will also mean that ongoing and complete communications are necessary for the implementation team, senior management, and the staff.
The Purchasing Process
The purchasing of LNG equipment (or any new technology equipment) requires several steps in chronological order as follows:
• Homework – investigate the options and available products as well as exactly what is needed including funding. • Specification – determine the appropriate specifications for the equipment needed. • Order – send out requests for proposal and award a contract for the equipment desired. • Installation – have the equipment delivered, installed, and tested/verified that it is working properly.
As with any purchase, homework is required to learn about the product options for what you wish to purchase and to match those options to what will best fit your operation. You will also need to study your own operation and fully characterize the requirements for the equipment purchases. This can be done internally or by hiring a consultant experienced in preparing and choosing equipment for LNG operations; however, the transportation company should remain in the lead and control of the implementation. The ultimate goal in this process is for the fleet to
12 operate LNG vehicles in a cost-effective manner as soon as possible, this requires that the fleet become their own expert in LNG vehicle and infrastructure as soon as possible. Figure 1-3 shows an LNG bus at Dallas Area Rapid Transit (DART) in Texas.
Figure 1-3. LNG Transit Bus at DART in Dallas, Texas
Resources: Heavy Vehicle and Engine Resource Guide, U.S. Department of Energy/National Renewable Energy Laboratory, NREL/TP-540-31274, 2002. Natural Gas Vehicle Purchasing Guide, RP Publishing, 2002. NGV Resource Guide, RP Publishing, 2002.
Planning for Early Operations and Problems
As the start-up of LNG vehicle operation comes closer, plans are needed for resolving problems. Assurances of support from the vehicle and fueling vendors will be needed. These assurances should come in the form of having technical staff available to be on-site or be able to provide quick on-site support for problems that arise. The testing of infrastructure equipment and vehicle equipment should be done with only a few vehicles first to work all the final issues out. During all of these activities, the user should have personnel watching and learning about the problems and how to troubleshoot those problems in the future. These activities will be an extra expense, but will be required to optimize the operation in the future. Some sites have had significant issues during start-up that have required days, weeks, even months to resolve.
13 Training and Safety
The training aspect of LNG operations is also extremely important. All personnel should be aware of the considerations associated with the fact that LNG is a cryogenic liquid as well as a fuel. Personnel who work around or handle LNG should be required to be trained in the proper handling, what to expect, and how to react in case of an accidental spill or vapor release. When using a new fuel and with new equipment on-site, it is important that all personnel are provided with complete and accurate descriptions of the new facilities and receive proper training and information. Further information on training can be found throughout this Resource Guide, but especially in the subsection, What Are the Safety Considerations for LNG Vehicle Operations?
How Do We Resolve LNG Problems?
Over the course of any new system implementation, problems will occur. LNG is no exception to this rule. As most fleet mangers have probably experienced, any change to the daily fleet operations, even a change as small as implementing a new scheduling or route assignment process, can cause difficulties. These difficulties are magnified when they can have safety ramifications in addition to performance ramifications. The key to addressing these problems when they occur is to anticipate them before they occur. By considering how you would address the many types of problems that can occur with an LNG vehicle operation, you will be better prepared to answer the question: What do I do when my LNG systems don’t work?
The best way to prepare for all of the possible problems that may arise concerning LNG vehicle operation is to consider the types of problems that may occur and develop strategies for approaching each problem. When a problem occurs, the first objective will be to determine what the problem is. In order to do this, you must have knowledgeable personnel available to analyze the problem. Training is emphasized throughout this resource guide, but when problems occur is when it will pay off most. Developing as many on-site experts as possible will allow your fleet to address issues quickly and effectively to minimize vehicle downtime, and enhance performance. It is also important to make sure that training is kept up-to-date and personnel are familiar with the basic concepts of LNG vehicle operation and what to do if there is a problem.
An emergency plan, which is discussed further in What Are the Safety Considerations for LNG Vehicle Operations?, will address many of these issues. Most of the other issues concern the functionality of vehicles and equipment. Solving these problems will require accessing the proper information, personnel, and equipment. There may also be short-term solutions, which will enhance productivity, such as using spare vehicles or alternate fueling sites. It should be noted that LNG vehicles will vent fuel if not used regularly.
Another important thing to remember when implementing LNG vehicle operations is that this new technology is in the early stages of development. The responsibility will often fall on the operator to solve their own problems and analyze their own systems. It is very important for the fleets to embrace the new technology, not only learning as much as they can about LNG vehicles
14 in general, but also studying the patterns and behaviors of their particular systems and operations to improve overall performance.
What Are the Safety Considerations for LNG Vehicle Operations?
Like any fuel, safe handling procedures, and proper safety precautions must be followed when working with LNG. Many years of experience using NGVs have proven that natural gas can be used safely as a fuel for vehicles. However, using LNG, or any alternative fuel, involves different safety issues than most fleet personnel are accustomed to. The key to safely operating LNG vehicles is considering the procedures, equipment, and training that must be implemented within an LNG vehicle operation. Safety and training should be enhanced by using an architect and engineering firm experienced in LNG for site planning, facility modifications, installations of equipment, and emergency procedures. Training should include expert training available from third parties and vendors. The local codes officials and fire safety personnel should also be included in planning, training, and emergency preparedness exercises.
Effects of LNG Characteristics on Safety
Any consideration of the safety considerations for LNG vehicle operation must include an examination of the characteristics of LNG and how they affect safety considerations. A more detailed discussion of LNG characteristics can be found in the subsection What is LNG? Derived from natural gas, LNG is a clear and odorless liquid that, like other forms of natural gas, is not toxic, corrosive, carcinogenic, or a threat to soil, surface water, or ground water. If LNG fuel is spilled, it will dissipate rapidly into the atmosphere, causing no lasting problems for the soil, plants, or animals. Still, LNG vapor can create hazards if they collect in flammable concentrations. Besides vapor ignition, the major safety concern when working with LNG is exposure to cryogenic temperatures, because LNG is a cryogenic liquid. Section 2 discusses more deeply the safety issues related to LNG characteristics.
Keeping in mind the characteristics of LNG is important to avoid hazardous incidents while operating LNG vehicles. Until recent years, LNG had a poor safety image as a result of one accident. In 1944, a tank at a large bulk storage facility ruptured and caused a fire. Following that accident, safety codes were written to prevent future accidents. As long as the safety codes are adhered to, LNG can be safe for vehicle use. For the past several decades, the LNG industry has had significantly fewer accidents than conventional fuel refining and distribution facilities. For further information on the 1944 incident and two other incidents attributed to LNG see “A Brief History of U.S. LNG Incidents” at: www.ch-iv.com/lng.
LNG Codes and Standards
Based on knowledge of LNG characteristics and the experiences of the LNG vehicle industry, several codes and standards have been developed to provide guidelines for the design, production, and modification of LNG vehicles, fueling facilities, maintenance areas, and parking
15 structures. These standards provide an important independent reference to help assess the safety and reliability of equipment designs and facilities modifications. The major LNG codes are listed below:
• NFPA 57 Liquefied Natural Gas (LNG) Vehicular Fuel Systems Code, 1999 Edition • NFPA 59A Standard for the Production, Storage, and Handling of Liquefied Natural Gas (LNG), 2001 Edition • SAE J2343 Recommended Practices for LNG Powered Heavy-Duty Trucks, issued January 1997
NFPA 57, NFPA 59A, and SAE J2343 are the primary codes and standards that apply to LNG. These standards are not necessarily required by law. Organizations such as NFPA (National Fire Protection Association) and SAE (Society of Automotive Engineers) create these standards as guidelines, but they are only enforceable as law if a particular state or local government adopts them. Certain states such as Texas and California have developed their own codes1, though they often are similar to the standards discussed earlier. It is important to know what code if any is enforceable in your area. Even if no codes are enforceable in your area, consideration should be given to specifying that vehicles, fueling stations, and associated structures to conform with at least one of the standards described earlier. In most cases, the codes officials in your area will often have the final say for all buildings and operating facilities. This is why it is so important to include these officials and fire marshals in planning and execution of your LNG operating program.
Potential Hazards Associated with LNG
Like any fuel or any new vehicle technology, there are potential hazards. As long as users are aware of these hazards, they can be accounted for in vehicle and facility design. The specific hazards associated with LNG are discussed in detail in section 2, but a brief list is included here:
• Ignition Sources • Contact with Fuel • Asphyxiation • Pressure Increases Due to Vaporizing LNG
Vehicle Specifications
When vehicles are ordered or designed, they should be specified with at least a minimum level of safety characteristics. In addition to safety features designed into the vehicle, the vehicles must
1 Railroad Commission of Texas, Regulations for Compressed Natural Gas (CNG) and Liquefied Natural gas (LNG) Available at: www.rrc.state.tx.us/tac/16ch13.html California Code of Regulations, Department of the California Highway Patrol (CHP) Title 13, Division 2, Chapter 4, Article 2, Compressed and Liquefied Gas Fuel Systems. Available at: ccr.oal.ca.gov/
16 be operated and maintained in a safe manner in order to avoid hazardous incidents. The material in Section 2 highlights the major vehicle related safety features and practices that are necessary to safely operate LNG vehicles.
For safety purposes, vehicles should be specified to adhere to all applicable codes and standards. This includes any enforceable state or local codes that may apply in your area. LNG vehicles should also be specified with the performance characteristics to perform their intended tasks adequately. This increases safety by preventing the vehicles from being regularly pushed to their performance limits. Using vehicles in a more rigorous manner than they were designed for decreases reliability and can compromise safety. Additional information on specifying vehicles is included in How Do We Get Started?
Resource: Reference Guide for Integration of Natural Gas Fuel Systems, 2002, GRI-02/0013.
Vehicle Operation and Maintenance
After the vehicles have been designed, built, and delivered, there are many important elements involved in keeping LNG vehicles operating safely. Section 2 includes material that presents the major facets of safe LNG vehicle operation and maintenance. Other information sources and training should also be consulted for further information regarding these issues as well as other potential issues.
Fueling Stations and Other Facilities
LNG fueling stations and other vehicle facilities should be designed with many safety features. These features are typically designed to prevent pressure buildup, unsafe fuel releases, fires, and exposure to cryogenic materials. The implementation of these features and the ability of on-site personnel to properly respond to emergency situations will minimize the potential for costly or dangerous incidents. Figure 1-4 shows LNG fueling connectors for fueling a transit bus.
Transporting LNG
LNG is typically transported to the fueling station by truck, similar to conventional vehicle fuel distribution. LNG tanker trucks would be unlikely to rupture, because LNG is transported in a double-walled tank that is stronger than the tanks used to deliver other fuels. The likelihood of a rupture of an LNG container is small unless the pressure relief equipment or system failed completely or an unusual combination of events were to take place (e.g., loss of insulation, along with obstruction of the venting and pressure relief system).
17
Figure 1-4. LNG Fueling of a Transit Bus
Emergency Response
Important to a facility is the development of an emergency response plan. Even when employees are well trained, facilities are well designed, and proper safety procedures are followed, unforeseen accidents may occur. Events such as natural disasters, fires, power failures, or simple human error may present the facility with an emergency situation. If the emergency is not handled correctly, lives may be lost, property may be damaged, and lasting damage to the environment may occur. A good emergency response plan will contain the situation and bring things back to normal as soon as possible. Section 2 includes a detailed description of the main components of an emergency response plan.
Safety and Training
Safety and risk considerations of any fuel for transportation are voluminous, especially if it is new to the facilities and operation. It is important to ensure that personnel are trained to know the properties of LNG and to know proper safety procedures pertaining to LNG fuel and vehicle use. Personnel involved in the fueling and/or use of LNG vehicles, including but not limited to mechanics, drivers, supervisors, engineering staff, and fueling personnel, should receive training in the proper use of LNG. This training may be obtained from supplier schools, original equipment manufacturers (OEM), mechanic schools, and internal training. LNG safety procedures should be integrated into the existing facility standard operating procedures (SOP).
18 Is LNG Readily Available?
As noted earlier, natural gas is abundantly available from both domestic and North American suppliers. At projected levels of consumption, natural gas supplies will meet U.S. demands for at least 60 years, with non-conventional supplies capable of providing an additional 200-year supply. There is significant LNG production capacity in the United States in addition to significant LNG transported here from outside the United States by large ships. Government forecasts suggest that LNG will be readily available for the foreseeable future and also suggest that its price is likely to remain competitive among transportation fuels.
In local terms, while a network of public natural gas fueling stations is developing for CNG, public LNG fueling stations are not yet available in most areas. In the near term, LNG will be best suited for fleet vehicles that return to a central facility for fueling, though this may change in the long-term if public LNG fueling stations become available. Such a network could develop in some areas if current efforts to build and distribute small-scale liquefaction plants are successful. One such network being developed in the western U.S. is the Interstate Clean Transportation Corridor (ICTC).
North American LNG Production and Distribution
Most LNG in the United States is produced at storage locations operated by natural gas suppliers and at cryogenic extraction plants in gas producing states. In most cases, these suppliers produce LNG and store it for use during periods of high winter (heating) demand for natural gas. The process of adding natural gas from LNG (or other gaseous hydrocarbons) to the normal distribution lines during periods of high demand is known as “peak shaving”. In a 1998 report by Zeus Development2, 120 facilities in the United States were identified as producing LNG as part of normal operations. A handful of the large-scale liquefaction facilities in the U.S. provide LNG fuel for transportation uses (see the map below, Figure 1-5). These suppliers have capacities normally ranging from 50,000 to over 600,000 gallons per day. A fleet of 100 transit buses would be expected to use approximately 5,000 to 8,000 gallons of LNG fuel per day.
Current Availability vs. Potential Availability
It is estimated that about 7,566,000 gasoline gallon equivalent (GGE) of LNG are used annually within the U.S. for transportation fuel. As stated earlier, in the United States, 120 plants produce or store LNG as part of their normal operations. Of these, 59 generate LNG for peak shaving applications and seven plants sell LNG for motor fuel use. Consequently, there is a significant capacity in the United States for producing LNG that could be tapped for motor-fuel purposes if the market demand were to increase. In most of these cases, these plants can be readily shifted to LNG production if there were sufficient economic incentive. One of the major barriers is available and reliable transportation to the fleet’s site at a reasonable cost. Small-scale
2 Zeus Development, LNG Vehicle Markets and Infrastructure, GRI-98/0196, 1998.
19 Painter, WY Shute Creek, WY Hammond, IN
Sacramento, CA Satana, KS Ignacio, CO Chesapeake, VA Topock, AZ Trussville, AL
Chocolate Bayou, TX
Figure 1-5. Locations of LNG Production Plants in the U.S.
liquefaction, described in more detail in Section 2, may also add significant LNG motor fuel capacity in the future if commercially successful.
Local Availability Issues
LNG is typically purchased directly from the producer by the load or a long-term contract. The transportation of the fuel is contracted separately from an LNG shipping company. JB Kelley is one example of a company that delivers LNG. Most operators purchase LNG in truckload batches of roughly 10,000 gallons delivered 2 to 4 times per week depending upon fuel usage. Transportation costs often make up a significant portion of the cost of LNG, and it is generally not economical to transport LNG farther than 500 miles in any direction from the LNG production location.
Sources of LNG
There are several different techniques for creating LNG. It is important to understand the source of your LNG and how the operations of that source could affect the availability of LNG. The current and potential means of LNG production are listed below:
20 • Peak Shaving Plants • Nitrogen Rejection Units and Other Industrial Plants • Small-Scale Liquefaction • Landfill Gas
Issues to Consider for LNG Availability
The supply network for LNG motor fuel is not as mature as that for conventional fuels. There is the potential for interruption of supply for a variety of reasons. Hence, when implementing LNG vehicles in a fleet, special consideration will be needed concerning LNG supply and transportation. Issues to consider include:
• Guarantee of supply from the producer • Supply during scheduled and unscheduled shutdown of the production plant • Potential backup supply in case of scheduled or unscheduled loss of production • Regional availability of transportation (tanker trucks) for fuel • Transportation interruption – potential for labor strikes or roadway blockage such as blocked mountain passes during cold weather • Added cost of backup supply and transportation in case of interruptions
What Will This Cost Me?
The general path to cost-effective implementation of LNG vehicles into your fleet will require doing your homework, creating a network of resources and contacts, working with experts in LNG, and building your own expertise in LNG. The costs associated with using LNG vehicles will differ in many cases from the costs associated with conventional vehicles. The cost of the LNG will generally be lower than diesel on an energy equivalent gallon basis. However, this lower fuel cost may not translate into overall savings because natural gas engines generally have lower fuel efficiencies than diesel engines. The optimal situation for achieving reduced fuel cost with LNG is in high-mileage, high-speed applications. There may be cases where the price of LNG will be low and translate into significant cost savings.
Experience has shown that once maintenance personnel become familiar with maintaining LNG vehicles, the maintenance costs associated with LNG vehicles are typically only slightly higher than those costs associated with diesel vehicles. To overcome the additional costs associated with purchasing and operating LNG vehicles, fleet mangers may be able to obtain funding from federal, state, and local governmental agencies. In addition to funding, there may be tax breaks associated with the use of LNG that fleets can also take advantage of.
Although using LNG may require additional economic burdens even with funding incentives and tax breaks, fleets should consider the value of using environmentally friendly vehicles. This environmental contribution can help improve the image of your organization in the eyes of your employees, your customers, and your surrounding community. This subsection will outline the costs that may be associated with implementing LNG vehicles. All of these costs should be
21 carefully considered before committing to using LNG, but fleet managers should consider the benefits of LNG as well.
Truly determining the costs of using LNG will require taking a close look at the options available in your area and the necessary costs that will impact your individual fleet. The following suggested tasks, organized by the aspects of operation that they pertain to, will help you to understand what your costs will be and help you to make final decisions.
Vehicles
• Identify representatives available from engine, vehicle, and fuel manufacturers who can help with initial planning, problem solving and trouble-shooting. This can save you hours of staff time during the planning, start-up phase, and full-scale operations. • Estimate the power needs and range of your specific vehicles. • Decide how to stage the purchase, replacement, and delivery of the new vehicles. • Clearly define the operational differences related to the new fuel (e.g., how operations will change with regard to training drivers, fuelers, and maintenance personnel, as well as range, fuel availability, and power). • Calculate the usage of the vehicles (e.g., amount of fuel used per mile).
Facilities – Fueling, Maintenance, and Others
• Examine the effects of using LNG on your current site layout. • Determine the cost to modify or construct vehicle maintenance and storage facilities. • Determine the size of the fueling station(s) and type of fuel storage facility. • Solicit fuel cost estimates and select a preferred vendor. • Determine the staff time and cost of regulatory preparation steps, obtaining permits, consulting with safety and fire officials, and addressing building codes.
Operations and Training
• Examine the cost of training (and retraining) personnel involved in operating, maintaining, fueling, or supervising the new fleet. • Develop methods to track the fuel, performance, maintenance costs, and personnel issues for comparison with vehicles using gasoline or diesel fuel. • Determine potential roadblocks or problems and prepare workarounds in advance. • Ask representatives of companies that recently installed an LNG facility what lessons they learned during the process of switching to and using LNG.
The cost of operating an LNG fleet will vary depending on location, preparedness, and size of operation. By gathering enough information, however, fleets can begin to grasp what costs will be associated with using LNG vehicles and making them successful. Section 2 provides
22 additional information about cost factors; training personnel; short- and long-term cost increases; as well as capital investments.
Where Can I Find More Answers?
There are several sources available to provide answers to many of your questions. These sources include companies that supply LNG, consultants who provide advice to potential users of LNG, and companies with fleets powered by LNG. Additional information and lists of LNG suppliers, consultants, and fleets using LNG in routine operations are available in this guide.
Several federal and state government web sites, and the U.S. Department of Energy’s Alternative Fuel Data Center (AFDC) web site provide access to alternative fuel reports, brochures, analyses of LNG demonstrations, and documents and publications that may be useful. Here are web site addresses that may be useful for fleet managers who are considering adding LNG vehicles to their fleets:
• Alternative Fuels Hotline: 1-800-423-1DOE • Alternative Fuels Data Center: www.afdc.doe.gov • DOE’s Office of Transportation Technologies: www.ott.doe.gov • DOE’s Office of Transportation Technologies, Heavy Vehicle Projects: www.ctts.nrel.gov/heavy_vehicle or www.ctts.nrel.gov/ngngv • Clean Cities Program: www.ccities.doe.gov • California Energy Commission—About Natural Gas Vehicles: www.energy.ca.gov/afvs • California Air Resources Board, Moyer Program: arbis.arb.ca.gov/moyer/moyer.htm • Calstart: www.calstart.org/fleets • National Association of State Energy Officials: www.naseo.org/energy_sectors/stateenergy (click on alt fuels) • Natural Gas Vehicle Coalition: www.ngvc.org (especially the NGV Resource Guide) • Cummins Westport: www.cumminswestport.com
23
Topic, Page SECTION 2 Why Alternative Fuels? 24
What Is LNG? 34 THE SCIENCE How Do We Get Started? 57
How Do We Resolve LNG Problems? 78 & DETAILS
What Are the Safety Considerations For LNG Vehicle Operations? 81
Is LNG Readily Available? 101
What Will This Cost Me? 108
Where Can I Find More Answers? 116
What’s In This Section?
This section provides more details about alternative fuels, federal regulations, incentives offered to encourage the use of alternative fuels, LNG’s operational requirements, advantages and disadvantages, and use of LNG as a transportation fuel. Background information about LNG is also included, e.g., where LNG comes from, what the fuel’s properties are, fueling infrastructure, and on- board fuel systems design.
Why Alternative Fuels?
There are several reasons to consider the use of alternative fuels. These reasons will usually include all or a combination of the following: local and/or federal regulations require my fleet to seriously consider the use of cleaner fuels, local and/or federal incentives make the use of alternative fuels attractive for my operation, and the fuel cost and cost of alternative fuel operation in conjunction with incentives makes the use of alternative fuels attractive. Many fleets also can take advantage of the positive impression that the use of cleaner burning fuels can bring from the public and local regulators to their operation such as for garbage trucks and transit buses.
Alternative vehicle fuels have been available as long as gasoline and diesel fuels. However, in the early stages of vehicle development diesel- and gasoline-powered vehicles won out and have been the conventional vehicles of choice for nearly 100 years. Today, transportation vehicles use approximately 68% of all the petroleum consumed in the U.S. and account for about 27% of the total energy consumption in this country3. Over the past decade, the return to alternative fuels has been accelerating due to government incentives brought on by environmental and energy security concerns.
Natural gas has been the alternative fuel of choice for the transit bus market and the medium- and heavy-duty truck market. The number of compressed and liquefied natural gas vehicles (NGVs) has grown steadily over the past 10 years (see Figure 2-1)4. For example, a survey performed in 2001 by the American Public Transportation Association (APTA) reported the following:
• 5,147 (9.3 percent) of the 55,190 buses in the APTA survey were powered by an alternative power source. • The majority of those alternative fuel buses were powered by natural gas (4,979 buses or about 97 percent). • Among the 4,979 buses powered by natural gas were 842 powered by liquefied natural gas (LNG), and the remainder was powered by compressed natural gas (CNG).
The APTA survey includes about 300 transit agencies and represents about two thirds of the transit buses in the U.S.
Web Site References: Energy Information Administration: www.eia.doe.gov American Public Transportation Association: www.apta.com Bureau of Transportation Statistics: www.bts.gov
3 Davis, S., Transportation Energy Data Book: Edition 21, Oak Ridge National Laboratory, October 2001. 4 Alternatives to Traditional Transportation Fuels 1999, Energy Information Administration (EIA).
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Alternative Fuel Descriptions
The definition of alternative fuels may vary slightly depending on the state where the vehicle is used. Here is a summary of alternative vehicle fuels in use today:
• Natural gas (compressed and liquefied)—Natural gas is a mixture of hydrocarbons and is produced either from gas wells or in conjunction with crude oil production. Natural gas has been used for many years as a vehicle fuel by U.S. utility companies. Natural gas is widely used in residential, commercial, industrial, and utility markets—and, since the 1980s, has become a transportation fuel. It has become a popular alternative fuel because of its domestic sources and growing commercial and public availability through an existing network of natural gas pipelines. The chemical components of natural gas are methane, a relatively unreactive hydrocarbon, other hydrocarbons such as ethane and propane, and other gases (such as nitrogen, helium, carbon dioxide, hydrogen sulfide) and water vapor.
The fuel can be stored on-board a vehicle in either a compressed gaseous state (CNG) or in a liquefied state (LNG). CNG fuel is odorized (a smell like rotten eggs); however, LNG is not odorized because the odorant would solidify in the cold temperature. LNG is produced by cooling natural gas and purifying it to a desired methane content. LNG is a popular alternative to diesel because it has a high-energy content per unit volume and is comparable to gasoline and diesel in time to fuel large vehicles. Additional information about LNG, is provided in the subsection titled What Is LNG?
120,000
100,000
80,000
60,000
Number of NGVs 40,000
20,000
0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 Year
Source: Energy Information Administration (EIA)
Figure 2-1. Growth of Natural Gas Vehicles Over the Past 10 Years
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• Alcohol fuels (ethanol and methanol)—Ethanol and methanol are the primary alcohol fuels available for vehicle use. While both fuels are alcohols, they have different feedstocks or sources. The Clean Air Act Amendments of 1990 mandated the sale of oxygenated fuels in areas with unhealthy levels of carbon monoxide, and this has increased the demand for alcohol fuels. Ethanol and methanol have similar chemical and physical characteristics. Ethanol, also referred to as ethyl alcohol or grain alcohol, is a clear, colorless liquid. It can be blended with gasoline (e.g., 10 percent ethanol and 90 percent gasoline) to increase the octane and decrease the emissions from gasoline. Ethanol blends in low percentages by volume can be used in all types of vehicles and engines that use gasoline. These blends of gasoline and ethanol are often referred to as gasohol. Ethanol vapors are relatively non-toxic compared to gasoline, according to studies. An ethanol blend of up to 85% by volume (E85) has been used in several OEM light-duty vehicles (especially since model year 1998).
Methanol, also known as wood alcohol, is produced by steam reforming natural gas to create a synthesis gas, which is then fed into a reactor vessel in the presence of a catalyst to produce methanol and water vapor. Synthesis gas is a combination of carbon monoxide (CO) and hydrogen that is fed into the reactor vessel under high temperatures and pressures where CO and hydrogen are combined. The reactor product is distilled to purify and separate the methanol from the reactor effluent. Alcohol fuels have achieved some success in vehicle use over the past two decades. However, this fuel is generally no longer in use. The last OEM light-duty vehicle to be capable of using a blend of methanol (M85, 85% methanol by volume) was the 1997 Ford Taurus.
• Clean diesel (biodiesel, ultra-low sulfur diesel, natural gas-derived diesel)—Clean diesel fuels may include biodiesel, special diesel formulations, such as ultra-low sulfur diesel (ULSD), and natural gas-derived diesel fuel from the Fischer-Tropsch process. Biodiesel is a replacement fuel made from natural, renewable sources such as vegetable oils. Biodiesel in small percentages by volume (usually up to 20% by volume – B20) can be used in compression-ignition engines without engine modifications, and has the energy level and range of diesel fuel. Used in a conventional diesel engine, B20 can result in substantially reduced emissions of unburned hydrocarbons (HC), CO, sulfates, particulate matter (PM), and other toxic air contaminants. Biodiesel by itself (B100) as a fuel can show higher oxides of nitrogen (NOx) and may require changes to the engine control. Diesel engine manufacturers should be consulted to determine the optimal usage of biodiesel.
Ultra-low sulfur diesel fuels (e.g., less than 15 parts per million [ppm]) are now being sold in several states. Studies show that ULSD allows the use of more active catalysts in conjunction with soot filters (diesel particulate filters – DPF). The function of the catalyzed filter is to remove PM, or soot, gaseous emissions, CO and HC, as well as the characteristic odor of diesel fuel emissions.
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Diesel fuel can also be made synthetically with a process such as Fischer-Tropsch, which processes natural gas into a fuel similar to diesel fuel with low sulfur and low aromatics content. This fuel has shown the ability to significantly reduce diesel engine emissions in studies.
• Electricity—With this fuel, mechanical power comes directly from electricity to power motors, which is quite different from the other alternative fuels that release stored chemical energy through combustion. The main benefit of an electric motor is there are no tailpipe emissions. The downsides are the initial capital cost and range limitations (typically 60 to 150 miles on a single battery charge). On-board rechargeable batteries (or potentially other energy storage devices such as ultracapacitors in the future) power the electric motor. Electricity used to power personal or fleet vehicles can be provided for battery charging by standard 110- or 220-volt outlets transferred to batteries, e.g., lead-acid, nickel cadmium, nickel iron, or sodium nickel chloride. Full charges take four to eight hours but special 440-volt outlets can charge to 80 percent in less than an hour. Special training may be required to operate and maintain electric vehicles.
A new alternative fuel propulsion technology for heavy-duty vehicles currently being demonstrated and tested uses batteries coupled with a diesel engine powering a generator to recharge the batteries. This technology is known as diesel hybrid electric propulsion and can significantly extend the range of an electric vehicle. Hybrid electric vehicles allow the use of regenerative braking. Regenerative braking takes advantage of the energy that is normally turned into heat during braking by converting it into electrical energy. This energy can then be stored in the vehicle batteries and used later to power the vehicle. This technology prevents some energy losses providing greater fuel and energy efficiency, which can reduce emissions. This type of braking can reduce wear of the brakes as well.
• Hydrogen (for fuel cells and internal combustion engines)—Fuel cells fueled by hydrogen have been used to power electric equipment on spacecraft for many years. Fuel cell vehicles combine hydrogen fuel from the vehicle’s fuel tank and oxygen from the air to generate electricity that powers an electric motor, just like electricity from batteries does for a regular electric vehicle. When hydrogen and oxygen combine, they give off energy and water—but no emissions from the tailpipe except water. Gaseous hydrogen can be carried on a vehicle if it is compressed and stored in high-pressure containers, similar to the method used for CNG vehicles. Hydrogen can also be liquefied for on- board storage. There is also hope that on-board fuel reformers may be able to pull the hydrogen out of any fuel composed of hydrocarbons, such as gasoline, natural gas or methanol. Research funded by the U.S. Department of Energy is underway to develop, by 2004, highly efficient low- or zero-emission automotive fuel cell systems that can be powered by hydrogen, methanol, ethanol, natural gas, or gasoline.
Hydrogen can also be used directly in internal combustion (IC) engines to power vehicles. Hydrogen can be used in IC engines by itself or combined with natural gas. These technologies are in the relatively early stages of development, yet they have more potential to reduce emissions than any other internally combusted fuel.
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• Propane—Liquefied petroleum gas (LPG) consists mostly of propane, propylene, butane, and butylene in various mixtures. The mixtures in the U.S. are mainly propane, which is a byproduct of natural gas processing and crude oil refining. LPG’s components are gases at normal temperatures and pressures. Propane has the lowest flammability range of any alternative fuel and is a nontoxic, nonpoisonous fuel that does not contaminate aquifers or soil. Propane leaks are easily detected because an odorant (similar to rotten eggs) has been added. Nearly 270,000 vehicles—mostly in fleets—are currently using propane in light- and medium-duty vehicles, such as taxis, school buses, and police cars.
Blends of any of these alternative fuels with gasoline or diesel fuel, as well as other chemicals, may also be considered part of the alternative fuels group. These fuels are currently powering a variety of vehicles, including heavy-duty trucks, garbage packers, dump trucks, snowplows, package delivery vans, buses, taxicabs, and other passenger cars.
Web Site References: Energy Information Administration: www.eia.doe.gov U.S. Department of Energy, Clean Cities: www.ccities.doe.gov U.S. Department of Energy, Alternative Fuels Data Center: www.afdc.doe.gov
Legislative Drivers
The current focus on alternative fuels, cleaner air from mobile sources, and energy security has evolved significantly since 1988, due principally to substantial federal legislation. Government regulations to reduce air pollution and public concerns about harmful emissions from transportation vehicles are driving the use of alternative vehicle fuels. Using alternative fuels in transportation vehicles can reduce air pollution as well as the nation’s dependence on foreign oil, because most of the alternative fuels are widely available in the U.S. from relatively local sources.
Several acts that have renewed and sustained the interest in alternative fuels are:
• Alternative Motor Fuels Act 1988 (AMFA) • Clean Air Act Amendments of 1990 (CAAA) • Energy Policy Act of 1992 (EPAct) • Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) • Transportation Equity Act for the 21st Century of 1998 (TEA-21)
The provisions of the AMFA, CAAA, EPAct, ISTEA, and TEA-21, and other federal and state legislation require a gradual transition of some fleets from conventional fuels, gasoline and diesel, to alternative fuels. These regulations also include requirements for monitoring emissions and providing incentives to potential users of alternative fuel vehicles (AFVs).
Two federal agencies, the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Energy (DOE), have enabled and promoted the movement to AFVs. The EPA has been driving the use of alternative fuel by implementing more stringent mobile source
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emissions requirements. DOE has taken the lead among federal agencies in promoting the use of alternative fuels by funding or co-funding alternative fuel vehicle demonstration and evaluation projects. These alternative fuel projects help DOE to ensure energy security by promoting domestic fuel sources, and decreasing dependence on oil reserves in foreign countries.
During the late 1980s and early 1990s, federal agencies led the way by requiring federal fleets to transition to AFVs, many of which chose CNG. Many states followed with additional regulations and their own incentive programs to promote and increase the use of alternative vehicle fuels. The most prominent of these states is California, the state setting the pace for emissions regulations as well as incentive programs, although many others are following California’s lead.
Many of the emission-reduction goals in national legislation are based on purchases of alternative fuel vehicles as a percentage of total vehicle purchases. On that basis, the purchase of alternative fuel vehicles has not been as successful as originally envisioned. But the availability of alternative fuel vehicles has caused conventional fuel and vehicle providers to find ways to reduce vehicle exhaust emissions significantly in order to meet certification levels over the last 15 years and into the future, as shown in Table 2-1. The fuel providers and vehicle manufacturers have been extremely successful in reducing toxic exhaust emissions, while improving vehicle performance and safety.
In August 1998, the California Air Resources Board (CARB – the regulatory body in California for air quality protection) designated diesel particulate emissions as a toxic air contaminant (TAC). A TAC in California is defined as an air pollutant which may cause or contribute to an increase in mortality or in serious illness, or which may pose a present or potential hazard to human health5. Since CARB designated diesel particulate emissions as a TAC, the pressure on heavy-duty engine manufacturers to reduce particulate emissions has been severe. The U.S. Environmental Protection Agency has not followed suit with CARB; however, there is a general consensus that the reduction of diesel particulate emissions is extremely important for cleaner air. Many studies are under way to determine the severity of the toxicity issues with diesel particulate emissions.
Greenhouse gases (GHG) are another pressure on the reduction of heavy-duty engine (and all engine) emissions. Greenhouse gases generally include water vapor, carbon dioxide (CO2), methane (CH4), and oxides of nitrogen (NOx). The greenhouse effect is a natural process that keeps the surface of the earth warmer than the space surrounding the earth. Greenhouse gases in the atmosphere allow some of the solar radiation reflected off the earth’s surface to be re-emitted back towards the earth, rather than releasing all of this solar radiation back to space. The net effect is a warming of the earth’s surface and its lower atmosphere. Figure 2-2 shows a graphical representation of the greenhouse effect. Over the past 10 to 20 years, there has been growing concern with the increase in the concentration of the greenhouse gases, and the potential effect that these increases may have on the climate of the earth.
5 California Health and Safety Code, Section 39655.
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Table 2-1. EPA Emission Standards for Heavy Duty Engines
Model Year Exhaust Emissions (g/bhp-hr) Diesel Truck THC NMHC NOx CO PM 1991 1.3 5.0 15.5 0.25 1994 1.3 1.2 5.0 15.5 0.10 1998 1.3 1.2 4.0 15.5 0.10 2004a 1.3 2.4, 2.5b 15.5 0.10 2007 1.3 1.2 0.2 15.5 0.01 Diesel Transit Bus THC NMHC NOx CO PM 1994 1.3 1.2 5.0 15.5 0.07 1996 1.3 1.2 5.0 15.5 0.05 1998 1.3 1.2 4.0 15.5 0.05 2004a 1.3 2.4, 2.5b 15.5 0.05 2007 1.3 1.2 0.2 15.5 0.01 Federal Clean Fuel Fleet Vehicle Standards THC NMHC NOx CO PM LEV – Federal -- 3.8b 14.4 0.10 LEV – California -- 3.5b 14.4 0.10 ILEV -- 2.5b 14.4 0.10 ULEV -- 2.5b 7.2 0.05 a – These emissions levels have been moved ahead to October 2002 for OEMs included in an EPA Consent Decree b – 2.4 NMHC + NOx or 2.5 NMHC + NOx with a limit of 0.5 on NMHC
Table 2-1. Acronym List THC – total hydrocarbons NMHC – non-methane hydrocarbons NOx – oxides of nitrogen CO – carbon monoxide PM – particulate matter LEV – low emission vehicle ILEV – inherently low emission vehicle ULEV – ultra-low emission vehicle
e Rad er Sol h Greenhouse Gases p a s iation o r m At
Earth
Figure 2-2. Greenhouse Effect
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Since the start of the industrial revolution, carbon dioxide concentration in the atmosphere has increased 30%, methane has increased 100%, and oxides of nitrogen have increased 15%. Carbon dioxide is often considered the general indicator of increased greenhouse gases. Scientists generally believe that burning fossil fuels and other human activities are the primary reasons for the increased concentration of carbon dioxide. Fossil fuels are used to power cars and trucks and heat homes, businesses, and industrial centers. These fossil fuels are responsible for many other potentially toxic emissions. About 98% of the carbon dioxide, 24% of the methane, and 18% of the oxides of nitrogen in the atmosphere are attributed to the use of fossil fuels6.
Greenhouse gases and regulated emissions are produced from vehicles, stationary engines, and from the development and delivery processes of providing the fuels to market, called fuel-cycle emissions. From a greenhouse gas emissions standpoint, many believe that a given fuel must be studied from the extraction process through the actual use or combustion of the fuel in a vehicle in order to understand the full emissions impact and energy efficiency of using a fuel type. In order to properly evaluate energy and emissions impacts of vehicle technologies, the fuel cycle from “well to wheels” and the vehicle cycle need to be considered. The U.S. Department of Energy through the Argonne National Laboratory has developed a modeling tool to complete this type of analysis – the Greenhouse Gases, Regulated Emissions, and Energy use in Transportation (GREET) model. There have been some issues raised about model additions regarding inputs of this model in respect to sources of fuels such as natural gas in terms of domestic versus import sources and how the use of wind power for electricity would impact these analyses. As with any model analysis, you need to clearly understand the assumptions and the inputs of the model in order to interpret the results properly.
In response to the concerns with vehicle emissions, the standards for mobile emission levels are expected to become much more strict with a phase-in of reductions starting in 2007 (see Table 2- 1). These new standards will be especially strict on emissions of particulate matter (PM) and oxides of nitrogen (NOx). These standards will require that tailpipe emissions be significantly reduced from current levels by 2010, when the standards will be fully implemented. In order to meet these more difficult requirements, both diesel and natural gas engines will be required to change how NOx is controlled and what aftertreatment devices are used. Both diesel and gasoline fuels must reduce sulfur levels as well in order to enable the use of more active catalysts in aftertreatment devices. Today’s standard for diesel is 500 parts per million (ppm) sulfur, and the future standard will be 15 ppm sulfur by 2006. Vehicles will be allowed to use more active catalysts and aftertreatment devices, such as catalyzed diesel particulate filters (DPFs), because of the lower sulfur level in diesel fuel (called ultra-low sulfur diesel – ULSD). California, New York, and other parts of the country already have limited distribution of ULSD. The CARB has verified a number of catalyzed DPFs for on-road heavy-duty vehicles in California.
From an energy security perspective, results of the legislation designed to promote the use of domestically produced alternative fuels have been disappointing. There has been no significant reduction in dependence on foreign oil. In fact, consumption of petroleum-based fuels continues
6 EPA Global Warming web site, www.epa.gov/globalwarming/climate/index.html.
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to increase, and fuel economy for most light-duty vehicles (at least those vehicles classified as minivans and sport utility vehicles) has gone down as a fleet average. Although a large number of alternative fuel vehicles have been purchased, this has not had a significant impact on petroleum consumption because few of the light- and medium-duty alternative fuel vehicles that have been purchased are dedicated vehicles. Dedicated vehicles can operate only on the alternative fuel for which they were designed. Most of the medium- and light-duty alternative vehicles are bi-fuel (operates on the alternative fuel or conventional fuel) or dual-fuel (can use an alternative fuel, conventional fuel, or some combination). Surveys indicate that most alternative fuel vehicles that can operate on gasoline or diesel fuel, operate almost exclusively on those fuels rather than the alternative fuel7. The reluctance to use alternative fuels has been attributed to the lack of fueling infrastructure. In other words, there are not enough places to fuel the vehicles with alternative fuels, therefore, the drivers tend to use only conventional fuels.
Speaking before the U.S. Senate Committee on Finance (July 2001), Jim Wells (Director, National Resources and Environment, General Accounting Office) commented on the GAO’s position on the barriers to sustained alternative fuel vehicle introduction in the U.S. The barriers that have impeded the introduction of alternative fuel vehicles are as follows:
• The relatively low price of oil • Insufficient availability of alternative fuel refueling infrastructure • The relatively higher cost of certain alternative fuel vehicles
The U.S. Congress has supported and encouraged the use of alternative fuels through tax incentives with exemptions, credits, and deductions, yet AFVs have not been widely adopted. Jim Wells explains, “Alternative fuels and vehicles have not made much of a dent in the conventional fuel and vehicle dominance of the U.S. vehicle fleet, primarily because of the fundamental economic obstacles. As reported in the GAO report of February 2000, any significant increase in the use of alternative motor fuels and vehicles by the general public will depend on two main factors: (1) a dramatic and sustained increase in the price of gasoline and diesel and (2) very large incentives, far above the current levels, to reduce the cost of using alternative fuels and vehicles. Depending on what happens to conventional fuel prices, these incentives would likely need to be maintained for some time – at least until the number of vehicles reaches the level necessary to support an economically sustainable infrastructure8.”
Web Site References: U.S. Environmental Protection Agency (EPA): www.epa.gov/otaq/ California Air Resources Board (CARB): www.arb.ca.gov Intergovernmental Panel on Climate Change (IPCC): www.ipcc.ch U.S. Department of Energy, Office of Transportation Technologies: www.ott.doe.gov U.S. General Accounting Office: www.gao.gov U.S. Department of Energy/Argonne National Laboratory, GREET: www.transportation.anl.gov/ttrdc/greet/
7 GAO, Limited Progress in Acquiring Alternative Fuel Vehicles and Reaching Fuel Goals, Energy Policy Act of 1992, February 2000. 8 GAO, Impact on the Transportation Sector, Alternative Motor Fuels and Vehicles, July 2001, GAO-01-957T.
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Incentives
(Note: Most of the information about incentives in this subsection is excerpted from various web sites and some of it may be outdated, e.g., incentive amounts, grants, or government tax deductions. Please contact the Clean Cities Program Office in your state for current information. Clean Cities contacts in each state can be found by clicking the Clean Cities Coordinators link on the Clean Cities Contact web site: www.ccities.doe.gov/contact.shtml. Do your homework as well, tapping into the web sites of trade associations for the various fuels, federal and state agencies, fuel providers, and vehicle manufacturers. Web links for many of these sources are listed in Section 3−The Appendix.)
Several federal agencies offer financial incentives and in-kind support to increase the development, production, and sales of AFVs. The main federal incentives for purchasing or converting individual AFVs are the federal income tax deductions for clean fuel vehicles ($2,000 to $50,000), available through the Internal Revenue Service in the U.S. Department of Treasury. For example, a new qualified clean fuel truck or van with a gross vehicle weight of more than 26,000 pounds would qualify for an income tax deduction of $50,000. Income tax deductions are also available for installing refueling or recharging facilities for AFVs. There is also ISTEA/TEA-21 legislation for congestion mitigation and air quality (CMAQ) projects. The EPA has a voluntary diesel retrofit program that matches fleet operators, engine manufacturers, and local governments with providers of technology resources to promote the use of cleaner fuels.
DOE’s Office of Transportation Technologies (OTT) has developed guides and information to help fleet managers and companies make informed decisions and more easily switch to alternative fuels. The Fleet Buyer’s Guide—which is designed to help fleet managers understand the relevant regulations and incentives, based on their facility locations and company descriptions—can be reviewed or downloaded from the following web site: www.fleets.doe.gov.
DOE’s Fleet Buyer’s Guide includes a summary of federal tax credits, deductions, and incentive programs sponsored by DOE, EPA, the Federal Highway Administration within the U.S. Department of Transportation (DOT), and many states, which offer a variety of incentives to encourage fleets to switch to AFVs. The on-line version of the Fleet Buyer’s Guide allows state- by-state searches to identify incentives available from each state and related contacts for further information. The guide describes what AFVs are available, identifies where fueling stations are located, and provides the cost differences between using AFVs and conventional vehicles.
Another key source of information about incentives is a report released in February 2001 by the National Conference of State Legislatures (NCSL), entitled State Alternative Fuel Vehicle Incentives, A Decade and More of Lessons Learned. NCSL is a bipartisan organization serving legislators and their staffs in all 50 states and territories. NCSL’s objectives are to improve the quality and effectiveness of state legislatures, foster interstate communication and cooperation, and ensure the states’ strong cohesive voice in the federal system. The report is essentially a survey of Clean Cities coordinators and representatives from utility companies, government officials, manufacturers, and fleet representatives. There were 305 responses to the survey, 20 percent of those contacted. The report can be found in PDF format at the Alternative Fuels Data
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Center by searching for NCSL and can be purchased on the NCSL web site (http://www.ncsl.org/public/catalog/catdir.htm, then click on Public User and either click Transportation and scroll down or search for the title).
Many funding programs from the federal and state programs require a calculation of air quality savings based on using the alternative fuel vehicles. These savings would be based on the engine certification emissions levels from the EPA (www.epa.gov/otaq/certdata.htm) or California Air Resources Board (CARB) compared to the emissions levels provided in Table 2-1. These emissions savings calculations are described on the Moyer program web site at CARB – arbis.arb.ca.gov/msprog/moyer/moyer.htm.
The combined result of federal and state programs is that the air is becoming cleaner and both government and private sector fleets are expected to comply with required future emission regulations, which are expected to be much stricter beginning in 2007. Future legislated incentives may be significant, assuming they are approved. The current push by the natural gas and electric vehicle industries includes a 50-cents-per-gallon incentive for using alternative fuels. Descriptions of current and potential future incentive programs can be found on several web sites, including:
• U.S. Department of Energy, Alternative Fuels Data Center: www.afdc.doe.gov • U.S. Department of Energy, Clean Cities Program: www.ccities.doe.gov • Natural Gas Vehicle Coalition: www.ngvc.org • U.S. Environmental Protection Agency retrofit program: www.epa.gov/otaq/retrofit • California Energy Commission: www.energy.ca.gov/afvs/ • California Air Resources Board, Moyer Program: arbis.arb.ca.gov/msprog/moyer/moyer.htm • Calstart – Westart organization: www.calstart.org/fleets.
What Is LNG?
Before entering into the details of effectively operating LNG vehicles, some background information about natural gas, LNG, and their use as vehicle fuels is appropriate. Natural gas is abundant domestically and is used to heat homes and cook food throughout the U.S. Currently, there are over a million natural gas vehicles on the road worldwide9, and more new natural gas- powered vehicles are being produced every year. While most of these vehicles operate on compressed natural gas (CNG), the use of LNG vehicles is growing. Natural gas is a clean burning alternative transportation fuel available in adequate quantities today. It is composed primarily of methane (more than 85 percent) and other hydrocarbon gases, such as ethane, propane, butane, and pentane, as well as gases such as nitrogen and carbon dioxide.
9 Natural Gas Vehicle Coalition web site: www.ngvc.org accessed 12/12/01.
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Natural Gas Characteristics
Natural gas is available throughout the world, produced from wells or reservoirs of pure natural gas or petroleum with natural gas. These wells may contain other liquids and materials. Most petroleum wells contain a considerable amount of natural gas. When energy exploration companies drill a well, the natural gas may be captured for processing and sale, for re-injection into the well after petroleum and/or other chemicals are removed, or the natural gas may be flared (burned) or vented on-site.
In addition to conventional sources of natural gas, there also are non-conventional sources of natural gas. Many of the largest deposits of natural gas are in locations that are not accessible for large-scale sale and distribution. These deposits are called stranded gas reserves. Other natural gas sources include hydrated natural gas deposits in the oceans and natural gas from landfills. Hydrated natural gas is trapped within a lattice of water molecules in an ice-like form. Landfill gas can be recovered from existing landfills, but has a low methane content and a high concentration of carbon dioxide and other materials. The methods for retrieving these non- conventional sources of natural gas are still under development and are not yet commercially viable. However, if these sources, especially hydrates, could be accessed, the impact on the supply of natural gas would be substantial. The Department of Energy’s Office of Fossil Energy notes that the recovery of one percent of the potential domestic hydrate resources would more than double the domestic gas resource base.10
After considering the existing and potential sources of natural gas, we should look at how natural gas is processed and distributed. After retrieval of conventional natural gas, processing is required to separate the natural gas from other liquids and contaminants. First, the gas is separated from free liquids such as crude oil, hydrocarbon condensate, water, and solids. The separated gas is then further processed to meet specified requirements for natural gas transmission companies. Natural gas is distributed throughout the United States via extensive pipeline systems from the well to the end user. The system consists of long-distance transmission pipelines, followed by local distribution systems. Some high-pressure and liquefied storage is also used to help meet seasonal peak demands.
Natural gas is colorless and odorless, but odorants are typically added to gaseous forms of natural gas to aid in leak detection. Conventional odorants solidify at temperatures higher than those necessary to liquefy natural gas. For this reason, LNG typically does not contain odorant. The same liquefying process that prevents the use of odorants, serves to purify the natural gas fuel, meaning that LNG contains significantly fewer contaminants than pipeline natural gas, from which CNG is typically derived. A comparison of fuel composition of natural gas sources, as reported in the results of a GRI survey, is shown in Table 2-2.
10 Energy Information Administration, Natural Gas 1998: Issues and Trends, April 1999.
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Table 2-2. Average Natural Gas Composition in the U.S.
Pipeline Natural Peak Shaving LNG from a Nitrogen Component Gas LNG Rejection Unit Methane 81.3-97.5% 95.3% 97.5-99.5% Ethane 2.0-7.0% 4.1% <1% Propane 0.27-3.0% 0.43% <0.1% Butane 0.04-0.57% 0.08% Nitrogen 0.26-10% 0.02% 0.02% Oxygen 0-10ppm Carbon Dioxide 0.47-1.5% Water 3.5-20 lb/MMcf Sulfur 0-1.2 lb/MMcf
Source: GRI, “Variability of Natural Gas Composition in Select Major Metropolitan Areas of the United States,” MVE CD - Liquefied Natural Gas, Alternative Fuel of Choice ppm – parts per million MMcf – million cubic feet
Natural Gas as a Vehicle Fuel
Natural gas has proven to be a suitable vehicle fuel and is widely available within the U.S. Natural gas vehicles (NGVs) have been certified to perform in compliance with all current environmental emission standards (e.g., the Clean Air Act Amendments of 1990), including standards limiting PM, non-methane hydrocarbons (NMHC), CO, and NOx. There is an issue of higher methane emissions from a natural gas vehicle compared to a diesel- or gasoline-fueled vehicle. Methane is considered a greenhouse gas (discussed earlier) and the emissions of extra methane from vehicles is becoming more restricted in many parts of the world.
The major difficulty associated with using natural gas as a vehicle fuel is storing the fuel on- board the vehicle in quantities that will provide comparable ranges to gasoline or diesel vehicles. Two different approaches have been used to reduce the volume of the natural gas needed to fuel the vehicle, compression and liquefaction. When used as a vehicle fuel, compressed natural gas (CNG) is typically stored on board the vehicle at high pressure—up to 3,600 pounds per square inch (psi). When LNG is used as a vehicle fuel, it is typically stored at cryogenic temperatures, which may be as low as -260°F at pressures ranging from atmospheric to 200 psi.
Several private fleets began using CNG in the 1980s. Most of these fleets have their own on-site CNG fueling stations. Since federal incentives began in 1988, the number of NGVs and private and public fueling stations have increased and the use of natural gas vehicles has grown. Most of the growth has been for fleets but the number of individual vehicle owners operating NGVs has also increased. LNG vehicles in the U.S. have only come into significant use since the early 1990’s. Still, implementation of LNG vehicles and the experiences of LNG vehicle users are growing.
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In general, natural gas engines can be used with CNG or LNG. This is important because while LNG fuel system technologies may only be in their early stages, the natural gas engine technology used on LNG vehicles has been in use over the past two decades.
LNG Background
Liquefying natural gas and other gases began with a desire to liquefy air, mostly to get pure oxygen for use in chemical and metallurgical industrial processes. In the early 1900s, Dr. Karl Von Linde, a German scientist, invented a way to separate air by cooling it in stages under pressure until the various constituents (oxygen, nitrogen) condensed to liquid. Later, this process was used to separate minor components of atmospheric gases such as argon, krypton, and xenon, which were used in the manufacture of light bulbs. Refinements to this process in the 1930s led to the development of the U.S. propane (LPG) industry.
Godfrey Cabot was the first to apply for a patent in the United States to liquefy natural gas. The new process had several benefits. Liquefying natural gas could solve storage and transportation problems by condensing the gas to a liquid, which reduced the storage volume. The LNG could be re-vaporized, returning it to its gaseous state, and sending it through the natural gas pipeline when required to meet high consumption demands, such as during cold winter days. This process of re-vaporizing is known as “peak shaving,” i.e., shaving off the peak demand requirement for the incoming pipeline gas. The first LNG plants in the U.S. for “peak shaving” were built and started operation in the 1940s.
The ability to liquefy natural gas allows large quantities to be stored for seasonal peak shaving or shipped for import/export commodity activities. In the case of stranded gas reserves, natural gas sources not accessible for distribution, the natural gas must be liquefied for transport to market, sales, and distribution. The natural gas may be liquefied directly by cooling the gas to a cryogenic liquid, LNG. Beginning in the 1960s, special shipping vessels were built specifically for the transport of large amounts of LNG. The shipment of LNG required the construction of import and export terminals where LNG could be safely loaded onto the ship and then offloaded for storage.
Another way of liquefying natural gas is to change it chemically to another form that has a higher energy density per volume. The chemical conversion of natural gas to liquid is generally called gas-to-liquid (GTL) and has become an industry of its own. Natural gas may be used to create synthesis gas, which is made up mostly of carbon monoxide and hydrogen. Synthesis gas can be used to make synthetic diesel fuel (using the Fischer-Tropsch process) and other chemical products. These liquids can be shipped by conventional means, rather than cryogenically.
LNG Characteristics
As discussed earlier, the process of liquefying natural gas separates the natural gas from other components by cooling the natural gas in stages under pressure until the constituents of the natural gas are condensed to a clear liquid form. Most LNG is produced at storage locations
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operated by natural gas suppliers and at cryogenic extraction plants in gas-producing states. Many fleets that depend on heavy-duty vehicles—such as transit buses and trucks—are selecting LNG over CNG because more energy can be stored on board the vehicle in liquid form.
Liquefying natural gas into LNG creates a very compact form of natural gas. One cubic foot of LNG will vaporize into 618 cubic feet of natural gas at atmospheric pressure (618:1). LNG is nearly twice as dense as CNG. This is a major factor in the choice to use LNG in vehicles because it means that more fuel can be stored on board while taking up less space than CNG. This allows LNG vehicles to achieve comparable ranges to their diesel counterparts. It takes 1.55 gallons of LNG to provide the same energy content as a gallon of gasoline and 1.67 gallons of LNG to provide the equivalent energy of a gallon of diesel. For this reason, fuel or efficiency comparisons between LNG and gasoline or diesel are usually made on an equivalent energy basis.
LNG is purified before liquefaction to remove elements possibly transmitted in pipeline gas, such as condensable carbon dioxide and odorants. The condensable carbon dioxide, water, and other elements such as odorant (hydrogen sulfide) from pipeline gas are removed, because they would solidify during the liquefaction process. Then a cryogenic process of refrigeration and/or depressurization is used to liquefy natural gas. This process removes some of the heavier hydrocarbons, leaving mostly methane (85 to 99 percent). The resulting LNG is a clear and odorless liquid that is non-toxic, non-corrosive, and non-carcinogenic. Because of the purification process, which separates LNG from potential contaminants, natural gas fuel derived from LNG is much purer than pipeline natural gas (See Table 2-2).
Boiling Points of Common Industrial Gases
0 LNG Oxygen Nitrogen Hydrogen Helium Absolute Zero -100
-200
-259 -300 -297
Degrees Fahrenheit -320
-400 -423 -452 -460 -500
Figure 2-3. Boiling Points of Industrial Gases at Atmospheric Pressure
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LNG can be produced at a variety of chemical processing facilities, including: an LNG plant, where heavier hydrocarbons and carbon dioxide in the natural gas are removed; nitrogen rejection units (NRU), which remove nitrogen from natural gas; LNG import/export terminals; facilities where peak shaving is conducted; and other prototypes or experimental plants such as landfills, or synthesis gas and olefin plants. (For additional information on sources of LNG, see the subsection titled Is LNG Readily Available?)
The LNG purification and refrigeration process is not unique. Industrial gases, such as nitrogen, oxygen, and helium, are used in manufacturing, food processing, and hospital operations on a regular basis. These gases are transported as cryogenic liquids to maximize the loads that trucks can carry. As shown in Figure 2-3, several of these cryogenic products have a lower boiling point than LNG. However, all cryogenic liquids are very cold, and special procedures and training are required to handle them. While cryogenic liquids require special attention, there is extensive experience handling cryogenic liquids in the industrial gas industry. The industrial gas industry produces and transports cryogenic liquids on a daily basis, and LNG users can learn from their experience.
Table 2-3 compares the chemical properties of LNG with those of other fuels. Natural gas ignition requires mixtures in the 5- to 15-percent range. This flammability range is actually wider than some fuels, but since natural gas is lighter than air, it is likely to dissipate quickly. This makes LNG less likely than other fuels to ignite in an open environment. Spills of LNG will rapidly dissipate (rise) in the atmosphere as natural gas, which is buoyant at temperatures above -160°F. However, released natural gas will rise and can be trapped in ceiling pockets.
The properties shown in the table below are described in the following definitions. There are many other properties that could describe these fuels, only a few were chosen here.
Boiling Temperature – The temperature at which a liquid boils. This temperature is usually given at atmospheric pressure (0 psig). Pure methane boils at –259 °F at 0 psig. The boiling temperature increases as the pressure increases. At 100 psi, pure methane has a boiling temperature of about –200 °F. BTU (British Thermal Unit) – A BTU is a measure of heat energy used to describe the heat released upon combustion of any substance. BTU is the quantity of heat energy that must be added to one pound of pure water to raise its temperature one degree F. Fuel Density – The mass of fuel per volume. Fuel density and fuel energy density are directly related. As the fuel density increases, the fuel energy density increases. Autoignition Temperature – The lowest temperature at which a substance will ignite without having an external ignition source. At this temperature, ignition can occur from heat alone and not from a spark or flame. Pure methane has an autoignition temperature of 1202 °F. Flammability Range – A substance or fuel requires the proper mixture with air to burn. The flammability range describes a range of volume percent of fuel in air in which burning can occur. Below the lower limit of the flammability range (lower flammability limit – LFL), there is not enough fuel to burn. Above the higher limit of the flammability range, there is not enough air to support combustion. Lower Heating Value – The amount of energy contained in the fuel. Fuel heating values are usually described as higher heating values (HHV) or lower heating values (LHV). The difference between HHV and LHV depends on whether or not the latent heat of vaporization of the water formed from combustion of the fuel is included. If the latent heat of vaporization of water is included, then the HHV or gross heating value is used. If the water formed from combustion is not included, then the LHV or net heating value is used. In transportation in the U.S., the LHV is generally used and is shown in the table on a mass and volume basis.
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Source of definitions: Murphy, M.J., 2000, “Motor Vehicle Fuels: Properties and Specifications”, Battelle. Murphy, M.J., 1994, “Properties of Alternative Fuels, Federal Transit Administration”, FTA-OH-06-0060-94-1. GRI/SAIC, 1992, “Introduction to LNG Vehicle Safety”, GRI-92/0645.
Table 2-3. Chemical Properties of Natural Gas and Other Fuels
Pure Property Methane LNG CNG LPG Diesel Gasoline Formula of the major chemical CH4 CH4 CH4 C3H8 C3 to C25 C4 to C12 component(s) Boiling -259 -259 -259 -44 370-650 80-437 Temperature, °F Fuel Density @ 1.07 (at 60°F [excluding atmospheric 1.58 3.53 4.22 6.7-7.4 6.0-6.5 RLM, LNG] pressure) (at 3500 psi) (lb/gal) RLM: 3.54 Autoignition 1202 1004 1004 850-950 600 495 Temperature, °F Flammability 5% - 15% 5% - 15% 5% - 15% 2.2% - 9.5% 1% - 6% 1.4% - 7.6% Range, vol. Lower Heating 21500 20200-21500 20200-21500 19800 18000-19000 18000-19000 Value (BTU/lb) Lower Heating 23005 Value (BTU/gal) RLM: 72700-77400 31900-33800 84500 128400 115000 76100 Specific Gravity 0.129 (at atmospheric @ 60°F 0.435 0.192 0.508 0.81-0.89 0.72-0.78 pressure) RLM: 0.428 RLM – Refrigerated liquid methane Source: Alternative Fuel Data Center, ALT, and Battelle
Methane Number – There is one more topic of interest on describing a fuel for use in an engine – motor octane number and methane number. These two numbers are used to describe the tendency for a fuel to knock (early or pre-ignition) in a spark-ignited engine. Motor octane number is most likely familiar based on ratings used for gasoline used in light-duty vehicles. Methane number has been developed to better describe knock tendency of gaseous fuels like natural gas. “The motor octane numbers were determined using a procedure (from ASTM), which uses isooctane and n-heptane as the reference fuels, where 100% isooctane equals 100 octane number and 100% n-heptane equals 0 octane number. The methane number scale is based on the molar percents of methane and hydrogen, with neat methane equal to 100 methane
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number.”11 In both cases, the higher the octane and methane numbers the better expected knock performance (or less knock tendency) of the fuel.
This discussion on methane number is important because specifications of fuel quality required for spark-ignited natural gas engines are many times based on methane number. Recently, there has been a push to reduce the methane content requirement for LNG so that more supply can be used in transportation. Currently, most LNG vehicle users require very high methane content (>98%). This higher methane content for LNG is intended to reduce the effects of weathering of the fuel. With more potential sources of LNG for vehicle use being made available, there is a need to relax this methane content to one that is more similar to the CNG methane content level, which is usually around 85% methane content or more. The lower methane content can also lower the price of the LNG. Current requirement for Cummins and DDC natural gas engines is around a methane number of 65 or better/higher. Your LNG supplier can provide the methane number for LNG fuel that they can supply. Note that the lower the methane content, the more vigilant that users will need to be in understanding weathering of LNG and minimizing the effect. LNG weathering is discussed in more detail later in this subsection.
Resources: Ryan, T., Callahan, T., Effects of Gas Composition on Engine Performance and Emissions, GRI-91/0054, 1991. Kubesh, J., King, S., Liss, W., Effect of Gas Composition on Octane Number of Natural Gas Fuels, SAE-922359, 1992. Liss, W., Thrasher, W., Natural Gas as a Stationary Engine and Vehicular Fuel, SAE-912364, 1991.
LNG Saturation
Saturation is one of the most difficult concepts associated with LNG vehicle operations. Saturated substances often behave opposite of what one might expect. Unlike gases, which increase in density under higher pressures, saturated liquid-vapor mixtures are less dense at higher pressures. Understanding saturation is critical to assessing the use of LNG and the amount of LNG stored on a vehicle or in a storage tank. Without understanding saturation and pressure issues, fuel storage systems can appear to “create LNG” because more higher-pressure gallons are dispensed to the vehicles than the number of gallons delivered to the storage tanks at near ambient pressures. The higher-pressure gallons are less dense and contain less actual fuel energy than the lower-pressure gallons. The following discussion of saturation should help to clarify the confusing saturation issues.
LNG is stored on-board a vehicle as a saturated liquid-vapor mixture. This means that the mixture is in between the liquid and vapor phases, so it will boil when heat is added and condense when heat is removed. To understand LNG saturation, it is helpful to briefly consider the process of refrigerating natural gas to make LNG. As heat is removed from the gas, its temperature decreases. This continues until the gas becomes so cold that it begins to condense to a liquid. The temperature and pressure at which this occurs is called the saturation point. Both
11 Southwest Research Institute, Effects of Gas Composition on Engine Performance and Emissions, GRI-91/0054, 1991.
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the gas (which is usually referred to as a vapor in this state) and the liquid that starts to form are said to be saturated. At this point, removing heat will cause more vapor to condense to liquid, but will not reduce the temperature as long as the pressure is held constant and the natural gas is not completely condensed, or liquefied. The temperature at which this transition from vapor to liquid takes place is called the saturation temperature.
In commercially available LNG fuel systems, fuel is stored on-board vehicles under saturated conditions, because it reaches an equilibrium of liquid and vapor through boiling and condensation. As stated earlier, a saturated liquid-vapor mixture typically boils when heat is added and condenses when heat is removed. The example of boiling water in a teakettle or pressure cooker is often used to explain saturation. It is well known that water boils at 212°F (100°C) at atmospheric pressure. But, at higher pressures, water must be heated to a higher temperature before it begins to boil (this is why a “pressure cap” is used on automobile cooling system radiators, forcing the pressure in the radiator to increase before the cap allows the coolant to overflow into the coolant reservoir). The saturation temperature increases as the pressure increases. Water already at a high temperature can also be made to boil by decreasing its pressure (vapor generation in this fashion is sometimes called flashing). The pressure at which the water starts to boil is the saturation pressure.
The same is true for natural gas as it is for water. The saturation temperature for condensation or boiling depends on the pressure. Conversely, the saturation pressure for boiling or condensation depends on the temperature. The relation between saturation temperature and saturation pressure is shown in Figure 2-4. This is known as the saturation curve or saturation line.
Figure 2-4 applies if the natural gas (and LNG) is 100% methane. When natural gas contains other constituents, the saturation temperature (or pressure) changes slightly as more vapor is condensed to liquid, or liquid is boiled to vapor. Also, the concentration of non-methane constituents is different in the liquid and vapor phases. If the non-methane constituents have a higher boiling temperature than methane, they may be more concentrated in the liquid phase. This phenomenon is called “weathering” or “enrichment” in some situations.
When natural gas is saturated, the liquid phase usually has a much higher density than the vapor phase. The dependence of this density on the pressure and temperature is indicated in Figures 2- 5 and 2-6, by the difference in density between the triangle to the far right of the figures and the circle to the left of the figures. It should be noted that these points lie on the broken-line curves labeled “saturation line.”
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0
-50 VAPOR
-100 Saturation line F ) ο -150
-200
Temperature ( LIQUID
-250
-300 Atmospheric pressure
-350 0 100 200 300 400 500 600 700
Pressure ( psia )
Figure 2-4. The Saturation Curve for Natural Gas (100% methane), Defines the Conditions Where the Liquid and Vapor Phases Can Coexist (Note: °F = 1.8°C + 32, 1 psi = 6.90 kPa).
In Figures 2-5 and 2-6, the triangles to the right denote the state of the liquid in the LNG fuel tank, which is assumed to be saturated at a typical pressure of 100 psig (690 kPa). The corresponding saturation temperature is -200°F (-93°C). Note that the liquid density at this state is 23.0 lbm/ft3 (368 kg/m3), which is nearly twice the density of a full CNG fuel tank. The higher density of LNG relative to CNG is the main reason that LNG is preferred for many heavy- duty vehicles with high fuel consumption and limited space for fuel tanks. On the other hand, CNG is more convenient for light-duty vehicles and many medium-duty vehicles, because fueling is simpler and there are no issues associated with cryogenic materials, fuel vaporization, and venting.
The circles on the left side of Figures 2-5 and 2-6 denote the state of the vapor in the LNG fuel tank ullage, which is saturated at the same temperature and pressure as the liquid. As discussed under the heading Normal Vehicle Operations later in this subsection, this vapor is fed to the engine when the economizer valve opens to reduce the LNG fuel tank pressure.
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700
600
NG to engine Saturation line 500 at 70οF & 100 psig
400 LNG in fuel tank, saturated at 100 300 psig
NG vapor in fuel tank ullage, Pressure ( psia ) 200 saturated at 100 psig
100 LNG vaporized and then warmed through "vaporizer"
0 0 5 10 15 20 25
Density ( Lbm / ft3 )
Figure 2-5. Pressure-Density Conditions of LNG Fuel Systems
100
NG to engine 50 ο at 70 F & 100 psig 0 F ) ο -50 Saturation line LNG in fuel tank, -100 saturated at 100 psig
-150 LNG vaporized and then warmed through "vaporizer" Temperature ( -200
NG vapor in fuel tank ullage, -250 saturated at 100 psig
-300 0 5 10 15 20 25
Density ( Lbm / ft3 )
Figure 2-6. Temperature-Density Conditions of LNG Fuel Systems
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The path shown from the triangle to the circle to the diamond in Figures 2-5 and 2-6 denotes the change experienced by the LNG as it is warms in the vaporizer. Its temperature and pressure remain constant at saturation conditions until all the liquid is boiled to vapor. As more heat is added in the “vaporizer,” the gas temperature increases (Figure 2-6), and the density decreases slightly.
Figures 2-5 and 2-6 illustrate an additional issue pertaining to LNG fuel system design. Note that if the LNG could be stored at a lower saturation temperature and pressure, its density would be greater and so more fuel could be stored in a given-size fuel tank. However, for current- generation LNG fuel systems, it is convenient to store LNG at a saturation pressure slightly more than the engine fuel pressure requirement. This simplifies the system because no fuel pump is required, but it also involves compromises including the quantity of fuel that can be contained in the fuel tank.
LNG Vehicles
A basic description of LNG vehicles can help to understand the issues involved with vehicle operation and maintenance. In many ways, LNG vehicles operate in the same manner as conventional vehicles. Both types of vehicles operate using an internal combustion engine and are driven in the same manner. The major difference between LNG vehicles and conventional vehicles is the LNG fuel system, which accepts and stores cryogenic fuel, warms and regulates the fuel, and delivers the fuel to the engine in gaseous form. In the text that follows, a basic LNG fuel system, its components, and its operation are discussed. The fuel system considered here is of a general nature and based on the Chart/NexGen Fueling LNG fuel tank design. Some aspects of this fuel system design may not be directly applicable to the vehicles you are operating or considering. It is important to understand the operation of your specific vehicles. This basic fuel system description is intended to provide the framework from which to build an understanding of the operation of the vehicles in your fleet. Figures 2-7 and 2-8 show LNG vehicles at Raley’s in Sacramento, California.
Fueling Operations – Most LNG vehicle fuel tanks are filled through a single hose and connection as illustrated in Figure 2-9. Although the details of the LNG fueling operation may be complex, they are automated such that the fuel hostler connects the fill hose to the fill connector and then activates the fueling cycle at the fueling station. The fueling station pumps LNG, which is typically at approximately 100 psi (690 kPa) and -200°F (-129°C), into the vehicle fuel tank(s). The fuel flows into the fuel connection and through the check valve, which only allows flow in a single direction, preventing the return of fuel to the fueling station. The liquid fuel is sprayed into the fuel tank through the fill spray header and into the vapor region in the fuel tank. The cooler liquid spray condenses (or “collapses”) the vapor so that the tank pressure does not increase as it is filled with liquid. The LNG tank is not to be filled completely. There is an ullage space, which allows for the expansion of the liquid as it heats up in the tank.
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Figure 2-7. LNG Trucks at Raley’s in Sacramento, California
Figure 2-8. LNG Yard Tractor at Raley’s in Sacramento, California
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Container 2 Manual Vent Connection Secondary Relief Valve, Not Vented Remotely
Venting Venting Primary Relief Valve, Vented r r o Check Control o
p Remotely to the Atmosphere Valve Valve p Va Va d Fueling i Check Valve
Liqu Engine LNG Fuel
Container